{ "system": "GoGuides Verified Text", "api_version": "verified-text-v1", "status": "ok", "response_type": "verified_text_record", "source_key": "britannica_1926", "source_title": "Encyclopaedia Britannica (1926)", "license_code": "public_domain", "attribution": null, "license_url": null, "chunk_id": "1926:earthquakes:346a013bb0f2", "title": "EARTHQUAKES", "section": null, "hash_alg": "sha256", "hash_sha256": "21753deb6bf87c3ec010e2f5e088352edcecbda1c3f10412ca291e42bbb7ee2b", "normalizer": { "name": "ggnorm", "version": "1.0" }, "verified_text": "seismology originally meant that department of knowledge which deals with earthquakes. up to about the end of the 19th century the meaning was almost unambiguous; the earthquake dealt with was the disturbance or quaking of the solid earth which could be felt and, when suf- ficiently severe, might cause damage or destruction. toward the end of the century it was found that certain very severe earth- quakes were accompanied by disturbances which could be regis- tered, with suitable instruments, far beyond the region where the shock could be recognised without instrumental aid, and not in- frequently these records could be obtained at great distances, even up to the antipodes of the origin. it is, however, only a very small proportion of the shocks which can be felt, not more than one in too, which give instrumental records at long distances from the origin; and it is probable, though not yet proved, that some of these long-distance records represent disturbances which nowhere were of a nature and severity that could be recognised except by delicate instruments. from the study of these long-distance records of unfelt dis- turbances, a new department of knowledge arose, which, being new and giving rise to some remarkable and surprising results, has rapidly grown in importance till, at the present day, it has almost usurped the title to the name seismology, though a large part of it does not concern the earthquake, as that word was originally understood. where the existence of the two branches is recog- nised, they have generally been distinguished as the old and the new scismology, but the new seismology is already an old and established subject of study and it seems better to distinguish them, when distinction is necessary, as teleseismology (rn de, gor distant) and engysseismology (eyyis, near), the former being the study of the long-distance records, the latter the study of the shock which can be felt near by the place of origin. the two branches are, and must remain in practice, almost distinct sciences, for the method and character of observation are very different in each case. duplex origin of earthquakes.—the connecting link between these two branches of seismology is to be found in the recognition of the duplex origin of certain great and destructive earthquakes, in which the destructive surface shock 1s of shallow origin and a secondary effect of a more deep-seated disturbance, which gives rise to the distant records. these have been named bathyscism and episeism, the former being applied to the deep-seated origin and the latter to the secondary shock originated near the surface. roughly, and with all the inaccuracy inevitable in a simile, they may be likened to the effect of the firing of a big gun; the explo- sion in the gun gives rise to a loud report which may be heard at long distances away, and may be taken to represent the bathy- seism and long-distance records, while the explosion of the shell which falls some distance away from the gun and causes the destruction desired, is the analogue of the episeism, or destruc- tive shock. thus prof. h. f. reid, from a study of the destruc- tive shock of the californian earthquake of april 18 1906, con- cluded that it originated at a depth of about 20 km., and dr. l. pilgrim, of stuttgart, studying the long-distance records, con- cluded that they originated at a depth of about 140 kilometres. these two very divergent estimates, obtained from different sets of data, by methods in each case sound and trustworthy, are easily reconcilable if the latter is regarded as referring to the bathyseism and the former to the episeism. . depth of origin —the depth of origin of the long-distance records has been the subject of several studies, and depths of so km. to 1,300 km. have been deduced. prof. h. h. turner concludes that the bulk of them originate at about 200 km. below the surface, that a small number start from greater depths down to about 600 km., mainly grouped round a depth of 500 km., while a still smaller number originate at lesser depths up to so km., and these are mainly grouped round a depth of about too kilometres. on the other hand, from the record of carthquakes which occurred in italy over a period of 14 years mr. r. d. old- ham finds that out of a total number of 5,605 shocks, more than 90% originated at depths of less than 10 km., and only 1% at depths of over 30 kilometres. cause of the episeism.—this strong contrast in depth is symp- tomatic of a difference in character of origin; the surface shocks which can be felt, or episcisms, are in some cases clearly due to the shock consequent on fracture of the rock composing the outer crust of the earth, and this is probably the usual cause of origin; but it is doubtful whether anything analogous to fracture, as we understand it, can take place under the great pressures and other conditions which must prevail at the depths where the bathyseism originates. cause of the bathyseism—the real nature of the bathyseism is still unknown, but in some cases, at any rate, and possibly, if not probably, in all, it is accompanied by a change of bulk, by which strains are set up resulting in distortion and fracture of the overlying rock near the surface. a possible cause is a regroup- ing of the chemical elements of a mass of deep-seated material, to form a new mixture of compounds, occupying a different volume from that which the original grouping required. chemis- try knows of many instances where an inert mixture of com- pounds may by change of temperature or pressure, or by some other external cause, change to a mixture of a new set of com- pounds, occupying a different volume. the most familiar instances of this are those known as explosives, in which the alteration of volume is very large and the change very rapid, but in other cases the action takes place more slowly, or the change of bulk may be much smaller. it is by no means impossible that similar changes take place in the interior of the earth, some slow and gradual, giving rise to elevation or subsidence of the land, others sufficiently abrupt to set up disturbances which are prop- aguted as elastic waves, and may give rise either to earthquakes 902 which can be felt, or to those which can only be registered by suitable instruments. interior of the earth——the study of the distant records has led to some interesting conclusions regarding the material of which our earth is composed. any disturbance of the nature of a shock will sect up two sorts of elastic waves which can be trans- mitted in a solid, one condensational and the other distortional, and these two forms of wave motion are distinctly recorded on all seismograms up to a distance of about too° from the origin, beyond which the second phase of distortional waves can no longer be recognised. from the times at which the arrival of these waves are recorded at the stations now scattered over the globe, it is possible to calculate the paths followed through the substance of the earth; this problem has been attacked by dif- ferent workers by different methods, and their conclusions, though diffcring in detail, are concordant in main features. successive layers of differing material.—the outermost layer of the earth is composed of material which transmits the conden- sational wave at about 53 km. per sec.; this extends downwards to a depth of some 50 to 60 km., and at that depth there is a rapid and great change to material of a very different character, in which the rate of transmission jumps to about 73 km. per sec., increasing steadily and continuously as the wave path pene- trates toward the centre of the earth, till a depth of about two- tenths to a quarter of the radius is reached. here the steady in- crease is checked, indicating a change in the character of the material traversed, but the increase in rate of propagation is again resumed, at a slower rate, till a depth of a little over three- tenths of the radius is reached and the rate of propagation has risen to 13 km. per second. from this depth the rate of propa- gation does not vary much at first, but beyond about a half of the radius from the surface, the rate of propagation decreases with increase of depth and at the same time the material traversed ceases to be able to transmit the distortional waves. other invesiigations—tyhese conclusions have an important bearing on, and receive confirmation from, the results of other lines of investigation. ‘the depth of 50 km. corresponds very closely with the depth at which the lower limit of the outer shell of cooled and solid rock, known generally as the crust, has been placed by geologists on physical and petrological grounds; the depth of about a fifth to a quarter of the radius, is that which would separate the metallic, mainly iron, central core from the outer shell of stony matter; the innermost nucleus, consisting of matter which is unable to transmit the distortional wave, had not been suspected before it was revealed by study of the distant seismograms, but is in accordance with the conclusion which has been reached by dr. h. jeffreys, from a study of the tidal retarda- tion of the earth’s rotation, that the central part of the earth is devoid of rigidity. | earthquake of sept. 1 1923.—the japanese earthquake of sept. 1 1923 ranks as the most destructive on record. ‘he roll of killed and injured is officially stated as 99,331 dead, 103,733 wounded and 43,476 missing; but an appreciable proportion of these casualties is attributable to the conflagration which followed on the earthquake, and was the cause of more than 95 % of the destruction of property, estimated as representing a loss of not far from_ {1,000,000,000. from the point of view of the maximum intensity of shock, or of the area affected by the earthquake, it ranks as a great, but by no means among the greatest on record; it is, however, of great scientific interest on account of the extent of the displacements of surface level which took place and the completeness with which these have been recorded. i changes of level.—the principal centre of the tokyo earthquake was under sagami bay to the south of tokyo, and soundings taken some months after the earthquake showed that the sea bed had been raised over large areas and depressed over others; the uplift gave soundings ranging to 135 fathoms less than had been recorded at the previous survey, and in the depressed area the depths had 1n- creased by as much as 259 fathoms at one place. the bulk of the depression amounted to 50 cu. km, (12 cu. m.) and that of the ele- vated tracts 20 cu. km. (4.8 cu. m.). as the size of the sea waves, which accompanied the principal shock, was not very great, it is certain that only a small part of these changes took place at the time of the earthquake, the greater part being probably due to the more gradual change taking place during the period of great instability, accompanied by very numerous after-shocks, which followed on the great earthquake, east, sir a.—east africa, operations in along the shores of the bay the changes of level were much less; except along a short length of coast line, the level of the land rose at the time of the earthquake, but the initial rise was not permanent and, within a month, gradually sank ti] the remaining uplift was less than half of the original. the most detailed observations were from misaki, where the original uplift reached the maximum re- corded figure of 25 ft., and a small island off the shore became part of the mainland; no change took place for the first four days, and then the land began to sink, at first by more than 2 in. a day but afterwards more and more slowly, till on sept. 26 the remaining up- lift was only 4 ft. 7 inches, changes of a siinilar character had been recorded in the cases of the cutch earthquake of june 16 1819, and the chilean of feb. 20 1835, but the records lacked detail and completeness, and have not been universally accepted. periodicity of earthquakes—the periodicity of earthquakes has long been a subject of study. in general, the attempt has been to find some connection between the frequency of occur- rence and some natural period such as the day, the year or the lunar month. with regard to the first two, the examination of the record from any region usually shows a distinct periodicity, the frequency of shocks reaching a maximum at some particular time of the day or year, and a minimum frequency at about half-way between the maxima, but when one district comes to be compared with another, and even when records separated by an interval of many years come to be compared with each other, no agreement can be found in the times of maximum and mini- mum frequency. some of the most recent work on this subject suggests that the true periods are not the day or year, but differ slightly from them, so that, in the course of a few hundreds of vears, the time of maximum frequency gradually works round the clock orcalendar. if this suggestion should be borne out by further work, it would prove that the earthquake is a purely terrestrial phenomenon and is uninfluenced as to time of occurrence by any cause exterior to the earth. — against this must be set one consideration which inclicates that the gravitational attraction of the sun and moon, though in no way a cause of the occurrence of the earthquake, may, to a small extent, have an influence in determining the exact time of occur- rence. if any record is examined, which contains a sufficient number of shocks to give a trustworthy average, it is found that the day shocks are slightly more frequent in summer, as compared with the general average for the year, and slightly less frequent in winter, while the reverse is the case with the shocks occurring during the night. as this is just what would be expected if the gravitational, tide-producing, stresses had some influence, and as the same relative disproportion has been found to be repeated, and to become more conspicuous, in those cases where the record has been discussed in terms of lunar hours and declination, it seems likely that the effect is in reality due to this cause. the smallness of the variation from average frequency, amounting to not more than 5% in general, is a measure of the slightness of the effect of these extra terrestrial influences. autnuorities.—the best general introduction to the subject is dr. c. davison, afanual of seismology (1921); g. w. walker, modern seismology (1913) is still useful as an introduction to the aims and methods of the modern development of the subject, of which a more elaborate treatment is b. galitzin, vorlesungen tiber seismometrie (1912). for subjects treated in this article the most important authorities are c. g. knott, ‘“‘ the propagation of earth- quake waves through the earth, and connected problems,”’ proc. hoy. soc. edin., vol. 39 (1919); s. mohorovicie, ‘‘ die reduzierte laufzeitkurve und die abhangigkeit der erdtiefe eines bebens ....” g. gerland’s beitrige 2. geophysik, vol. 13 (1913) and vol. i (1916); r. d. oldham, “ a seasonal variation in the frequency o earthquakes \" quar. jour, geol. soc., vol. 74 (1918), vol. 77 (1921); hf. 11. turner, brit, assn. seismol. committee reports of recent years, 1916, etc.; c. davison, “ the japanese earthquake of 1923, geog. jour., vol. 65 (1925); r. d. oldham, '' the depth of origin of earth- quakes,” quar. jour. geol. sac., vol. 82 (1926). (r. d. o.) east, sir alfred (1849-10913), british painter (see 8.827), was knighted in 19to, and died in london sept. 28 1913. east africa: see kenya colony; tanganyika territory. east africa, operations in.—when the world war broke out in 1914 the garrison of british east africa, the territory immediately north of german east africa, was scattered and engaged on punitive expeditions remote from the enemy frontier. in the case of each protectorate the troops were native with east africa, operations in european officers. the german forces, some 5,000 strong, includ- ing 260 europeans, lay ready to the hand of their commander, von lettow-vorbeck, a capable and determined soldier well able to employ them to full advantage. if it is remembered how keenly sensitive the native soldier is to any shortcoming in his superior and that von lettow had only been with his command for six months when hostilities began and kept that command efficierftt and formidable through four years of steadily declining fortune, some idea may be formed of the resolute nature and soldierly qualities of the german commander-in-chief. his operations consistently bore the clear imprint of his skill and personality, and there were advantages, other than his pro- fessional capacity and steady courage, upon which he could rely. i. early operations the country—nearly double the size of germany in 1914— which was the scene of operations, is for the most part covered by bush, dense as a rule, but occasionally thinning out to some- thing like park land. high mountain ranges, thick with vegeta- tion, rear themselves from bush and jungle which arc fever stricken and liable to wholesale inundation during the rainy season. rivers abound and malaria and dysentery of a malignant type, with other tropical discases, combined to swell the casualty list of a european or anglo-indian force. practically every animal imported into east africa for the use of the british forces suc- cumbei to the tsetse fly. the route of every british advance was marked by casualties duc to diseases from which the rank and file of the enemy—askaris recruited from local tribes—were im- mune. surprise by the attacker was as difficult as it was simple by the defender, who waited concealed and warned by the labori- ous approach of his adversary cutting roads and brid zing rivers. supply and transport presented appalling difficulties to an advance through hundreds of miles of naturally impenetrable bush, while the defending force slowly fell back upon the maga- zines posted in its rear. only an overwhelming preponderance in numbers made any advance possible, but a force starting with a strength adequate for an offensive enterprise constantly found itself reduced at best to an equality of strength on contact with the enemy. many good cards were thus in the hand of the ger- man commander; and he rarely failed to play them with full effect. naval operations and german adzvance-—on aug. 8 1914 two british cruisers, “‘ astraea”’ and “ pegasus,”’ arrived opposite dar es salaam from zanzibar, and, being unable to leave a garrison, the naval commander covenanted with the german governor that the latter should forbear from any hostile action in dar es salaam itself. parallel to the southern frontier of british east africa and about 50 m. distant from it ran the uganda rail- way from mombasa to lake victoria. this tempting and ex- posed objective, for the protection of which the british troops at the outset were hopelessly inadequate, at once appealed to von lettow, who on aug. 15 seized taveta, which lay in british terri- tory at the eastern end of the gap between the southern slopes of mount kilimanjaro and the northern end of the pare mountains in the german protectorate. an enemy force here was a standing menace to the british capital at nairobi, and, constantly raiding the railway line, seriously hampered the british initiative. in september the enemy cruiser ‘‘ kenigsberg ”’ returned to dar es salaam and on sept. 20 surprised and destroyed the ““ pegasus ” while undergoing repair in the zanzibar roadsteacl. a combined enemy opcration against mombasa, for the execution of which the “‘ kenigsberg ” was to attack the port in conjunc- tion with a land force moving north along the coast, failed, as the ** konigsberg ”’ was driven by the ships of the cape squadron into the rufiji delta, where she was run aground. the land force began its march along the coast on sept. 20, was repulsed at gazi, 25 m. from mombasa, on sept. 23, and retired to the frontier on oct. 8. the crew of the “ kenigsberg,” which was blown up in july rots, after being set on fire by the monitors ** severn ” and ** mersey,” joined the cnemy land forces, together with its armament of ten 4-1 guns. german raids along the coast, on the uganda railway, and into the frontier districts of uganda, belgian congo, rhodesia and j 903 nyasaland were constant in the opening months of the cam- paign. these small enterprises were much simplified by the central position of the enemy and the excellent lateral communi- cation afforded by the central railway from dar es salaam to kigoma, on lake tanganyika. this lake was under german control until dec. 1915, when by the operations of motor boats specially brought from capetown the enemy was deprived of the one lake which had not been in british hands since the earliest days of the campaign. reinforcements from india.—it soon became apparent that, unaided, the british protectorate forces could not hold their own, and the government of india consented to send an expedi- tion. on aug. 25 its leading unit reached mombasa with brig.- gen. stewart, who assumed command. the rest of the expedi- tionary force was directed on tanga, the northernmost german port, at the southern extremity of the usambara mountains, healthy highlands where the bulk of the german settlers resided. coincident with an attack on tanga an advance against moshi by the north of kilimanjaro was to be made by stewart. the expeditionary force under brig.-gen. a. e. aitken was about 7,000 strong and (except for the 2nd loyal north lancs.) com- posed of indian troops. failure of british offensive-—the transports reached tanga on nov. 2, when the local commissioner represented the place as an open and undefended port and bombardment was deferred. meanwhile, von lettow, advised of the plan by captured indian mails, was hurrying reinforcements to the coast. when one and a half british battalions landed two miles east of the town on the evening of the arrival, they met with strong opposition and fell back. von lettow arrived on the evening of the following day, when british reinforcements had been landed and fighting re- sumed, and on nov. 4 heavily defeated his opponent, whose casualties were 795. on the same day stewart, checked at longido, was compelled to retire. the british force at tanga re- embarked and reached mombasa on nov. 5. the first british offensive had thus failed completely. von lettow’s success at tanga put an end for the time being to any general offensive against him, and it was not until 1916 that the next british advance was set 1n train. the intervening period was occupied in raiding by both forces, with occasional engagements of a more ambitious nature. a british force was compelled to surrender on jan. 17 rors at jasin, in enemy territory, to a superior force, after 48 hours’ fighting, which exhausted their ammunition and water. german losses, especially in officers, were serious, as was the shrinkage of ammunition. maj.-gen. m. i. tighe assumed chief command in april rors and in june, bukoba, on lake victoria, was success- fully attacked. reinforcements arrive-—aid was now sought from a different quarter, for, with the conquest of german south west africa by gen. louis botha tn july 1915, the resources of the union of south africa became disposable to an extent which was impos- sible till the disappearance of the enemy from her own border. during the latter half of 1915 there was continuous preparation in south africa of troops, depets, supplies, medical stores, trans- port, animals and material of all kinds for use in east africa. by feb. 1916 one mounted brigade, two infantry brigades and one field artillery brigade, complete with all their auxiliary units, had arrived from south africa to join tighe. a second mounted brigade followed, together with a battalion of the cape corps (coloured men from the cape province). tighe also had the fol- lowing european units: the calcutta volunteer battery, the 2nd loyal north lancs., 25th royal fusiliers, 2nd rhodesians and two local settlers’ corps; india sent him from her native army 10 infantry regiments, one squadron of cavalry and two mountain batteries. the battalions of king’s african rifles were the original native protectorate force. at thesame time, von lettow’s force had reached the highest limit which it attained in the cam- paign and was probably over 20,000. the exact combatant strength is difficult to estimate, for there were many carriers of whom a percentage were armed and many trained as askaris. the askari in his own country is a soldier of high value. such a 904 force, with a strong leaven of europeans trained to arms, under a skilful and determined commander, was a formidable adversary in tropical bush country. german ammunition supplics—in april 1915 the mind of von lettow, which had been sorely exercised by his shortage of ammunition, was relieved in the following remarkable manner: a british ship, the “ rubens,” seized at hamburg, left that port loaded with arms and ammunition and appeared off tanga on april 4, being sighted by h.m.s. “ hyacinth.” entering manza bay on fire and abandoned, she was boarded by bluejackets, who found her timbered up and battened down. after firing more rounds the ‘‘ hyacinth ” steamed away on the assumption that her quarry would burn herself out. the germans returned and salved almost the entire cargo, and a largely increased volume of enemy fire from the mauser pattern 1898 rifles which the ‘“ rubens ” had brought was the result. a repetition of this opera- tion a year later will be referred to. ii. operations under general smuts the chicf command in east africa was assumed by gen. smuts in feb. 1916. he had previously declined the post, but when gen. smith-dorrien was compelled to relinquish the com- mand in consequence of illness he accepted it. he reached mom- basa on feb. 19 and found the railway completed from voi to serengeti, 5 m. from salaita hill, the german advanced position from taveta. a week earlier an attack on salaita had failed. the rainy season was at hand and movement would then become impossible, and smuts telegraphed to lord kitchener that he was ready to carry out the occupation of the kilimanjaro area at once. the proposal was agreed to and smuts proceeded to initiate his first advance. british advance on tavcta.—an attack, designed primarily to hold the enemy, was to be delivered on salaita by a force under gen. malleson, while stewart was to repeat his attempt of 1914 to reach moshi by the north of kilimanjaro and thence to intercept any enemy retirement in his direction. gen. van de- venter with a mounted brigade, moving by malleson’s right, was to cross the lumi river, and by way of the foothills of kiliman- jaro cut the enemy line of retreat between taveta and moshi. the execution of this movement unobserved was the only chance of surprising the enemy, for it was apparent to von lettow, who had made all preparations for retirement, that taveta was smuts’ objective. in the event it may be accepted that this surprise was effected. van deventer moved on march 8 and on the following day his troops were astride the moshi- taveta road. on the same day the germans evacuated salaita and took up new positions on two hills, latema and reata, cov- ering the gap between the pare mountains and kilimanjaro. the main enemy force was posted at himo, 5 m. from the gap, whence it could move in any direction to attack or retire. the progress of stewart’s force was so slow that his movement was without effect. the new enemy position was attacked on march 11 and, after severe fighting all day and the succeeding night, was occupicd on the morning of the rzth by a general advance in support of detachments which had won their way to the two crests during the night and caused a retirement by the enemy. german withdrawal.—von lettow now withdrew his entire force to a position (kahe-ruvu) which stretched south of the taveta-moshi road from kahe railway station eastward along the northern end of the pare mountains. he was followed up and attacked on march 18 from latema nek by brig.-gen. sheppard, and on march 20 van deventer was sent from moshi to turn the enemy at kahe. he seized kahe on march 2r and on the follow- ing night, after a very severe action with sheppard, the enemy withdrew tolembeni, 20 m. south of kahe. von lettow aban- doned one 4-1 gun, and had expended ammunition to an extent which he could ill afford, but his force was intact and the timely arrival of the second blockade runner at this juncture with four 4:1 field howitzers, gun and small-arm ammunition, machine- guns, stores, provisions and clothing was an inestimable stroke of good fortune. here the operations which smuts had under- east africa, operations in taken before the rainy season were successfully concluded and the british forces took up positions covering taveta and moshi and facing the enemy at lembeni. during the ensuing rains smuts reorganised his force and pre- pared to resume the offensive at the carliest possible date. ile could rely for assistance in his main operations upon the bel- gians in the northwest and the british force under maj.-gen. northey, operating from nyasaland, to the southwest. for reasons fully recorded in his dispatches, smuts decided at once to send van deventer with a mounted force rapidly by arusha to kondoa irangi and thence to the central railway and east along that line to morogoro. elis own force was to move south by the pangani, and make for the same ultimate objective, moro- goro. it was hoped that von lettow would there be brought to bay by the two converging forces. new british offensive—van deventer moved on april 3 and occupied kondoa irangi on april 19, capturing the enemy garri- son at lol kisale en route. he reached kondoa irangi after heavy casualties in men and animals from disease and was there cut off and reduced to immobility as a consequence of his losses and the advent of the rainy season. von lettow concentrated a force against van deventer and fighting ensued, but the ger- man attacks, with one exception, lacked vigour and were all repulsed. van deventer’s position was cased by the end of may, when smuts began his advance down the pangani and the bel- gians moved on tabora. maj. kraut was in command of the german force opposite smuts when the latter set his troops in motion southwards from moshi on may 18, von lettow having assumed direction of his concentration against van deventer. systematically outflanked by his opponent, whose main advance along the pangani was supplemented by flank move- ments by the pare and usambara ranges, kraut found himself compelled to leave the tanga railway and retire upon handeni. this place was scized by smuts on june 19, korogwe having been occupied four days earlier. on june 24 the germans were attacked simultaneously on three sides, but, after determined fighting, withdrew into the nguru ifills. smuts was now com- pelled to halt his force on the msiha river. in a month 250 m. had been covered, but malaria had reduced the strength of all units, combatant and non-combatant, in some instances to 30% of their original numbers. ‘the troops were on half rations, and the transport, which included a variety of types of motor ve- hicles, was much damaged. the coast region was now dealt with, and with the aid of the navy, tanga, pangani, sadani and bagamoyo were successively occupied between july 17 and aug. 15. the removal of the british base to tanga saved 200 m. of rail transport. dar es salaam was occupied on sept. 4, but three months elapsed from its capture before it could be used as the base. german reitrcat.—von lettow now moved the bulk of his force once more opposite smuts, and on june 24 van deventer resumed his advance and at the end of july held the central railway from kilimatinde to kikombo, about too miles. on aug. 9 he was ready to move on morogoro. the belgians were at the same time advancing on tabora against the german force under maj.- gen. wahle, who was left to do his best unaided, though some reinforcements were sent southwest against northey. smuts moved again on aug. 5, opposed by a detachment of the enemy whose main force was withdrawn to kilosa, whence it proceeded south towards mahenge, the eventual direction of the enemy retirement on all fronts. von lettow directed the remainder of his forces by a route through the uluguru mountains, thus foiling the attempt to intercept him at morogoro. heavy fight- ing ensued in these mountains but kisaki fell into british hands on sept. 15 and von lettow retired to mgeta river and there entrenched himself. on this front during the three last months of 1916, activity was confined to such minor affairs as are usual between opposite entrenched forces. civil administration was instituted in the occupied area behind the british forces. belgian operations —the belgian force (also native), under maj.-gen. tombeur with european officers, was divided into two brigades, the northern (col. molitor) and the southern east africa, operations in (lt.-col. olsen) and operated in the northwest of german territory, opposed by wahle, who was instructed to avoid a decisive action. the belgian operations, well planned and successfully executed, were of prime importance to the general campaign. broadly described, they were as foliows. molitor invaded ruanda by the north of lake kivu while olsen co- operated south of him by the north of tanganyika. the move- ments started on april 4, and by the end of may the belgians were in possession of ruanda. molitor then sent columns south- west to join hands with olsen and other columns southwest to lake victoria, which was reached on june 27. in the middle of july, on a front between tanganyika and victoria, molitor and olsen moved south on the respective objectives of tabora and kigoma, the terminus of the central railway on tanganyika. olsen occupied kigoma on july 28 and ujiji on aug. 2, and then moved east on tabora. co-operating with molitor was a british column under brig.-gen. sir c. p. crewe, who captured mwanza on the southern shore of lake victoria on july 14. on sept. 19 molitor occupied tabora which wahle had evacuated the previous day, leaving behind his sick with civilians and prisoners of war. crewe reached the central railway a weck later. british advance from rhodesia.—by this time northey had succeeded in interposing some of his forces, which were in three columns under lt.-cols. hawthorn, murray and rodgers (the last a south african unit), between tabora and mahenge. his advance was on an original front between lakes nyasa and tanganyika. murray occupied kasanga (bismarckburg) at the south end of tanganyika on june 8. the germans were defeated at malangali on july 24, and on aug. 29 iringa was occupied, lupembe having been seized ro days earlier. northey, ordered with van deventer, now at kilosa, to deal with the enemy in the mahenge district, was much outnumbered by forces already in touch with him and wahle’s columns approaching from the north, and on the night of oct. 21 most of wahle’s troops broke through him. on the same day kraut was heavily defeated at mkapira. hawthorn secured the surrender of an enemy column at ilembule. on dec. 24 van deventer and northey attacked the mahenge force. an enemy column surrendered to northey, but the force engaged with van deventer escaped him after fighting from dec. 25 to 28. position at end of 1916.—by the beginning of r917 smuts had evacuated 12,000 to 15,000 white troops (south africans), mostly victims to malaria, and they had been replaced by the nigerian brigade (brig.-gen. cunliffe) and fresh battalions of the king’s african rifles. kilwa and lindi, south of dar es salaam, had been seized by the navy and a force under ma}j.- gen. hoskins had been concentrated at kilwa. on jan. 1 1917 an advance was made on the mgeta position, but after heavy fighting the enemy retired across the rufiji at kibambawe. smuts now went to england and hoskins assumed the chief command. the rains ensued, and to clear the north bank of the rufiji was all that could be barely accomplished before opera- tions ceased perforce. hoskins completely reorganised his command, but before operations were resumed he was ordered to palestine. his successor in east africa was general van deventer, who assumed command of the forces there at the end of may 1917. ill. van deventer’s operations the enemy forces were disposed as follows: von lettow near kilwa, wahle in the lindi area, tafel at mahenge, detach- ments between kilwa and lindi, and near the ruvuma. northey lay south and west of tafel with another british force at iringa, northwest of the enemy. the rest of van deventer’s troops were to act against von lettow. in pursuance of this decision an advance was made by the kilwa force under brig.-gen. beves on july 5 towards liwale. the enemy fell back to narungombe, where a severe engagement took place on july 19. the encmy retired south, but the kilwa force was unable to move again until mid-september. in aug. the enemy was driven from the lukuledi estuary to allow of an advance inland from lindi. 905 the kilwa force (hannyngton) was to move south and that at lindi (beves) west. these operations were marked by the hardest fighting of the whole campaign. von lettow fell back, under pressure by hannyngton, towards nyangao, 40 m. south- west of lindi, wahle doing the same before beves. on oct. 15 a four days’ battle began between beves’ force and the enemy under von lettow joined by wahle. the latter retained their position and it was 10 days before beves’ force under the com- mand of cunliffe could resume the offensive. on oct. 8 tafel, pressed by northey with belgian co-opera- tion from the north, had retired from mahenge, and, breaking through two weak detachments on nov. 16, moved southeast towards von lettow, whom he was debarred from joining by the kilwa force. vainly endeavouring to join the main body, tafel reached the ruvuma, but, unable to procure food, sur- rendered with his entire force on nov. 28. germans retire to portuguese territory.—on the night of nov. 25-26 von lettow, having shed all weaklings, crossed the ruvuma into portuguese territory and thenceforward moved as the circumstances of his position, without bases and short of am- munition, dictated. early successes in the new sphere of action, especially at ngomano, gave the germans food, ammunition, arms and clothing, and when the rainy season set in in jan. 1918, they were able to rest for a short time. the operations during 1918 were carried out almost entirely by natives, the king’s african rifles, and von lettow fell back upon guerilla tactics. against him in portuguese territory were sent columns from the east and south shores of nyasa; and another (brig.-gen. edwards) advanced west from porto amclia midway between the ruvuma and mozambique. after various engagements von lettow marched in may south to the lurio river, 200 m. from german territory, captured ile, and in june reached the coastal region near quelimane. on july 1 he captured nyamakura, 25 m. from quclimane, and in the mid- dle of aug. at chalana, eluded envclopment by converging columns. ‘turning northwest, he was engaged by hawthorn (who had succeeded northey) at lioma, east of lake shirwa. after several encounters, the german force reached the ruvuma again on sept. 28 and, after resting at ubena, where wahle was left, set out for rhodesia. on nov. 1 von lettow made an un- successlul attack on fife and, turning southwest, took kasama on nov. g. advised on nov. 13 of the armistice, he accepted it the following day, and on noy. 23 formally surrendered to gen. edwards at abercorn. with him were dr. schnee, the gover- nor, and maj. kraut, together with a force of 30 oflicers and 125 other europeans, 1,165 askaris and 2,891 other natives (includ- ing 819 women), 1 small ficld gun, 24 machine-guns and 14 lewis guns. troops engaged, casualties, eic—the troops employed by the allies in east africa included 52,339 sent from india (5,403 british) and 43,477 south african whites. east african and nyasaland settlers, rhodesian volunteers and the 25th fusiliers numbered about 3,c00; african troops (king’s african ritles, nigerians, gold coast regiment, gambia company, cape corps) and west indians about 15,000; an approximate total of 114,000 not reckoning belgian native troops (about 12,000 in all), portuguese and the naval force engaged. the greatest number in the field at any one time, may to sept. ror6, was about 55,000; the lowest, in 1918, some 10,000, all african, save administrative services. british and indian casualties were returned at 17,823; of these 2,762 were 1n the south african forces. these figures are exclusive of casualties among carriers and of deaths and invalid- ing through sickness, which among the south africans alone excecded 12,000. the cost of the campaign to great britain, inclusive of indian and south african expenditure and that of the local protectorates to march 1919, was officially estimated at £72,000,000. bipliography.—j. h{l. v. crowe, general smuts’ campaign in east africa (1918); o. von lettow-vorbeck, aly remtniscences of east africa (1920) and jteia safart (tg2t); c. p. feudall, the hast african force (1921); see ulso world war: bibliograpily. (j. j.c.) 906 easter, fixed (sce 8.828).—the question of the date of easter has vexed the church for many centuries, and the difficulties which had arisen in determining the easter date led directly to the introduction of the gregorian calendar. the ecclesiastical astronomers of the middle ages exercised their ingenuity upon it for centuries, and made many elaborate tables. it is not proposed in this article to go into these very com- plicated matters, but to give a short summary of the more im- portant considerations, and to present some account of the subject in its more modern aspects. the celebration of the great spring festival is consecrated by the church to the commemora- tion of the central fact of the death and resurrection of our lord. this occurred at the time of the jewish passover. the jcws celebrated their deliverance from egypt by the feast of the passover. this was held on the 14th day of the first month of the jewish ecclesiastical year, which commenced with the vernal equinox, at the time of the full moon. the gospels record that our lord celebrated the passover on the thursday, while cai- aphas and the priesthood apparently celebrated it on the friday, the day of the crucifixion. as the jewish day is counted from sunset to sunset there may be some explanation of the difference in this fact, but when the festival of easter was established by the church, there was a sharp controversy between those who celebrated the event on the 14th day and those who celebrated it on the 15th, the quartadecimans, and the quintadecimans, which led to much bloodshed. the council of nicaea, held in a.p. 325, ecdel that easter should be celebrated on a sunday, but it was not till a.p. 716 that the english clergy submitted themselves to the papal rule, and that feeling ran high at the time may be judzed from the fact that ethelfrith, king of northumbria, massacred 1,200 monks at bangor, who adhered to the heresy of the 14th day. these acute religious controversies have long since died down, but the fact remains that we are left with a method of fixing the date of easter by which it can vary from year to year by no less than 35 days, between march 22 and april 25 (see 4.997). the date is fixed in accordance with the tables prepared by clavius for pope gregory niii., when he reformed the calendar on feb. 24 1582, and is an attempt to reconcile the solar with the lunar year, on the metonic system, with all the complications of the week, the month, the epact and an inexact calendar. the tables occasionally produce strange results. in 1923 the full moon of the heavens fell on the sunday given by the tables for the celebration of easter;and the resurrection, going by the real moon, was being celebrated before the crucifixion. proposals for fixing easter.—the inconveniences of an oscil- lating easter are felt by all sections of the community, as school terms, university terms, law terms and the great holidays of easter and whitsuntide are all affected by a moving easter. chambers of commerce, national and international, have since 1900 year by year passed resolutions in favour of a fixed date for easter. at the international conzress of chambers of com- merce held in rome in 1923 such a resolution was re-afirmed and addressed to the holy see. not long afterwards the matter was referred to the league of nations, and a conference was sum- moned at which the roman, the eastern orthodox and the anglican churches were represented, and it was agreed that there was no insuperable objection, on dogmatic lines to the fixing of easter, and it was abundantly proved that there was a prac- tically unanimous wish among the nations concerned that easter should be fixed. the movement in great britain.—on april 27 1921 lord desborough introduced a fixed easter bill in the ilouse of lords. under this, easter was always to be kept and observed on the second sunday in april, which was the date in 1925. the three main arguments in favour of the date were: (1) that it is the nearest sunday to the generally accepted date of the event which it commemorates; (2) that as the mean date of easter for 1oo years has been april 8-3, such a sunday complies to the full with the requisition that any date selected should fall within the present limits of deviation, and (3) it divides the christian year equally, and is a convenient date for the people. hkaster, fixed—eastern european front campaigns as regards no. 1 it may be stated that, though the matter cannot be absolutely decided, the balance of opinion seems to be that the crucifixion took place on friday, april 7 a.p. 30, so calculating by sundays, and in order to secure a date which can be very easily remembered, the second sunday in april would appear to be an appropriate one, but it would be still more accurate to make easter sunday on april 9, if that day were a sunday, or on the sunday following april g. certain ecclesias- tical difficultics would then be aided and there would always be 24 sundays after trinity, and the whole ecclesiastical calendar would be admirably fixed. the archbishop of canterbury stated in the course of the debate in the house of lords that as far as the anglican church was concerned it would be entirely accept- able to them that easter sunday should be a fixed sunday and not a variable one, provided that, among other things, the western churches were agreed. this evidently points to the holy see, which has admitted that no question of dogma is concerned. indeed the roman catholic bishop of salford has pointed out in a letter published in the tablet, that the dog- matic dangers and difficulties of the carly centuries involved in a change of the paschal calculation are no longer existent, and there can be no objection from the theological point of view. he also stated that it is a reform which has long been due, and that for the catholic church the holy see could make the change with a stroke of the pen. the supporters of the reform point out that the celebration of the birth of our lord was fixed in the 4th century by enact- ment for dec. 25, thus consecrating the old saturnalia of rome to the new religion, and that, this having been done, there is no good reason why the celebration of the death and resurrection should vary 35 days in accordance with a fictitious moon. the date of the celebration of easter is primarily a matter for the churches, and should be settled by them, but the inconveniences of a widely oscillating easter are felt in so many departments of civil life that it is to be hoped that the matter may be taken in hand without further delay. the possible alternative of fixing the easter and whitsuntide holidays independently of the church has been often mooted, but its use would be gencrally deplored. (d.) eastern european front campaigns.—this heading covers the story of the operations on the main russian front during the world war. it includes the campaigns in rumania, but not the serbian or salonika campaigns nor the russian campaigns in the caucasus against turkey. as the article is of such a general nature, its division into sections has been based on chronological sequence. the headings employed are there- fore i. the campaign of ro14; ii. the austro-german advance into russia, 1915; iii. rumania’s effort, 1916; and iv. the russian revolution, 1917. i. the campaign of 1914 theatre of war.—the theatre of operations after rumania had joined in the war, extended from the baltic to the black sea, a distance of some 800 m. in a direct line, or more than twice that distance if measured along the frontier lines between the opposing states. in aug. 1914 the actual iength of the frontier line along which the russian and austro-german hosts faced each other was over 1,000 m. from the baltic to the northern frontier of rumania, which was at this time neutral. this great length was due to the projection of russian poland as a huge salient between german east prussia and austrian galicia. the shape of the frontier, the great distances, and the physical features and communications, combined to divide the russian theatre into three “‘ sub-theatres ” until the russian retreat out of poland in ro1s. thus the operations in east prussia, in the polish salient and in galicia, though they formed part of a combined whole, had each their own special characteristics. the greater part of the huge area of operations was plain or — gently undulating uplands. the only heights sufhcient to con- stitute a serious military obstacle were the carpathians, which extended in a semicircle from the south-west corner of the eastern european front campaigns polish salient to the iron gate on the danube, forming a pro- tective barrier for the hungarian plains on the north and east. . opposite russia, they ran roughly parallel to the frontier and at 50 to 100 m. distant from it; opposite rumania they actually marked the fronticr. it was a constant aim of the russians thrcughout the operations, and the objective of rumania’s single abortive offensive, to pierce this barrier and reach the plains below. though there is only this one mountain barrier, the water barriers in the theatre are numerous and formidable. the most serious from the strategical point of view is presented by the marshes of the pripet (sometimes called the pinsk marshes or polyesie), an area stretching east from near brest-litovsk, some 200 m. long by 100 m. broad, where communications are few and military movements on a large scale extremely difficult in con- sequence. other water lines which had a considerable effect on operations are: in east prussia, the line of the masurian lakes; in the polish salient, the rivers vistula, narew, bobr, niemen and bug; in galicia, the dunajec, wislok, san and dniester; in the rumanian theatre, the danube itself, the oltu (aluta) and the siret (sereth). besides the rivers enumerated above, there were a number of lesser streams which influenced the course and direction of the operations. strategy in this theatre was in fact largely determined byrivers. rivers retard the move- ment of an advancing army but are seldom a permanent bar to its progress; though many of the principal river crossings had been fortified in peace, these fortifications had little influence on the course of operations, except, indeed, at przemysl. in east prussia and in poland were extensive stretches of forest, which had certain tactical consequences. the carpathians also were thickly wooded. the real key to the strategical moves on this eastern european front lay, as ever, in the communications. in this respect the con- trast between russia and her western neighbours was striking. in both railway and road communication russia was extremely backward, in spite of all her efforts in the years preceding the war to develop her strategical railways. the russian general staff had of set purpose prevented road or railway construction in the north and in the south-east of the polish salient in order to provide protection to a defensive position in the centre of the salient. this short-sighted policy seriously hampered russian strategy when an offensive campaign from poland was under- taken. nor could russia make much use of her great rivers as lines of supply owing to. lack of previous development. thus superior communications gave to her adversaries the inestimable advantage of greater mobility. characteristics of the armies —of the germans little need be said; their army of 1914 was probably the most powerful in- strument of war yet forged. the raw material of the russian army was in many ways excellent. the russian peasant in physique and powers of endurance surpassed the rank and file of other continental armies; he was easily disciplined and sto- ically brave. but his lack of individuality and want of education unfitted him for the strain of a long and unsuccessful war, and made him unduly dependent on good leading. this was not forthcoming once the original cadre of regular officers and n.c.o.s had fallen, since the russian system did not produce an efficient type of reserve officer. in organisation, the russian army was very weak on the technical side; the proportion of guns to rifles was smaller than in other armies; there were large masses of cavalry, provision for which threw a great strain on the communications, but which accomplished little. in no way except by weight of numbers could a russian army hope to gain the advantage over a german force. the austrian army, only slightly, if at all, superior to the russian on the technical side, was inferior to it in fighting quality. this was due to the heterogeneous nature of the austrian personnel, many of whom fought unwillingly and surrendered freely. a russian force was almost always the master of an austrian force of similar size, but required a great numerical preponderance to meet a force of germans with any hope of success. 907 the plans of campaign.i—the german plan of 1914 was a development of that drawn up by schheffen many years pre- viously. it provided for an offensive against france designed to obtain a rapid and decisive victory, and a defensive in the fast against russia until the decision had been obtained in the west. the choice of france for the initial offensive was actuated chietly by the relative slowness of russian mobili- sation and by the impossibility of gaining a rapid decision against russia owing to the great distances. the choice once made, germany’s problem in the east was to determine the minimum strength to be ieft for defensive purposes. this was eventually fixed at nine divisions, active and reserve, with one cavalry division, for the protection of east prussia; and certain second line troops for the defence of the eastern fortresses (such as posen, toritin [thorn], danzig, kenigsberg) and to watch the polish fronticr. the troops in east prussia, organised into four corps, formed the viii. army under prittwitz. the chief of the austrian general staff, conrad von hetzen- dorf, of some ability and of sanguine temperament, had planned an offensive into south-east poland between the vistula and bug rivers, directed on the line chelim (kholm)-lublin. this was to be carried out by the i. and iv. armies (dankl and auffen- berg). to protect their right flank and rear, the ii. and ii. armies (kevess and von brudermann) deployed east of halicz and lemberg. this offensive of conrad’s was originally designed as part of a combined austro-german offensive, in which ger- man forces from east prussia were simultaneously to attack on the narew line. germans and austrians were to meet about siedlce and thus cut off the whole polish salient. conrad had repeatedly urged this plan on moltke, but had failed to induce him to provide sufficient troops to take the offensive from east prussia, before france had been disposed of. in the absence of german co-operation, it is difficult to see what permanent success conrad could have hoped for from his che!m-lublin offensive, since, as already pointed out, the russians had neglected the communications in that area ex- pressly to embarrass the operation he had chosen. from the german point of view, however, this austrian offensive fitted in admirably with their strategic plan, since, whatever its out- come, it would keep the russians fully engaged and thus safe- guard the vital industrial areas of silesia, till the campaign against france had been won. the russians had gauged accurately the intentions of both their adversaries. their original plan was to take the offensive against the austrian armies in galicia and to act-defensively in the polish salient and against the germans in east prussia. they were, however, pledged to their i'rench allies to assume the offensive against germany at the earliest possible date. six armies were initially deployed in front line. the i. army (rennenkampf) assembled on the east frontier of east prussia, and the ii. army (samsonov) at warsaw. these two armies formed the north-western front, under jilinski. they were intended for action against the german forces in east prussia. the south-western front, under ivanov, consisted of four armies, of which the iv. (salza) and v. (plehve) were to deploy on the lublin-chelm railway to meet the expected austrian offensive; the iii. army (ruzski) and viii. army (brusilov) were to take the offensive at once from the eastern frontier of galicia in the direction of lemberg. it will be seen that the austrian and russian plans were almost the exact counter- part of each other. the grand duke nicholas assumed chief command of the whole russian armies. though no great strate- gist, he was shrewd and had a strong personality. his chief of staff, yanushkevich, was a man of no great ability or character. the russian strategy is attributed mainly to danilov, head of the operations branch of the general staff. in addition to the front line armies, the vi. army was assem- bled at petrograd for the protection of the capital and as a general reserve, the vii. army at odessa to watch the black sea coast, and an army in the caucasus to watch turkey. at the last moment, after mobilisation, a momentous change in the russian dispositions was made. the i. and ii. armies were 908 ordered to invade east prussia at once, without waiting to complete their concentration. this change was made solely to assist russia’s allies in the west. east prussia: august-september 1914.—rennenkamp!f’s i. army comprised 11 divisions and five cavalry divisions and samsonov’s it. army nine divisions and three cavalry divisions. they had thus in combination an overwhelming superiority over prittwitz’s viii. army, which was defending east prussia. combination between them was, however, completely lacking and led to their defeat in detail. jilinski, who was responsible for combining the action of the two armies, was a man of some administrative capacity but little aptitude for command. sam- sonov’s army had to move before its concentration was com- pleted, and was deficient in transport. the arrangements for obtaining and recording intelligence were indifferent in spite of the large masses of cavalry available; and so defective were the means of intercommunication that the russians were frequently forced to issue orders by wireless in clear, with the result that the germans often had complete information of their enemy’s moves and intentions. the course of events was bricfly as follows: rennenkampf crossed the frontier on aug. 17 driving back a german force at stallupenen; and on the 19th and 2oth, after a hard battle at gumbinnen, defeated prittwitz, who had concentrated against him the bulk of his army, leaving only one corps to observe the southern frontier. mcanwhile samsonov, stumbling slowly forward by mlawa, crossed into east prussia on the 2ist, causing prittwitz in momentary panic to announce his intention of withdrawing behind the vistula. he was promptly super- seded by hindenburg, with ludendorff as chief of staff. within a week the new commander had completely defeated the ii. army at the battle of tannenberg, surrounding and capturing the greater portion of it. receiving a reinforcement of two corps which had been hastily recalled from france, he then turned on rennenkampf, who had remained inactive during the disaster to the it. army, though faced by a small german detachment only. between sept. 7 and 13 he was attacked and driven out of kast prussia with very heavy casualties (see masurian lakes). in these opcrations the russians had suffered a total loss of some 250,000 men, a crippling loss in spite of russia’s immense reserves. a\\fuch war material had also been lost and this could not easily be replaced. on the other hand this invasion of ast prussia, by causing the recall of two corps from the west at the crisis of france’s fate, had made possible the victory of the marne. . operations in galicia, august-september 1914.— meanwhile the austrians in galicia had suffered heavy defeat at the hands of ivanov’s south-western group of armies. the offensive of their [. and 1v. armies towards lublin and chelm at first made satisfactory progress, battles at krasnik and komarew ending in their favour. but their flank guard of the it. and iii. armies was unable to withstand the onslaught of the russian iii. and viii. armics. on sept. 2 lemberg was lost and the advance of the victorious left wing was consequently stayed. two corps from the russian ix. army (which had been formed at warsaw as a central reserve) now reinforced ivanov’s right wing, and the whole austrian line was gradually pressed back. on sept. 11 a retirement to the san was ordered by the austrians; by the end of the month they had withdrawn to within som. of cracow, leaving their fortress of przemyel to stand sicge. first and second invasions of poland—the austrian defeat compelled the german supreme command to send direct assistance to her ally. this was done by the transfer of five and a half corps, formed into the dx. army, from east prussia to the front cracow—czestochowa, whence it advanced on warsaw in the jast days of sept. in conjunction with a simultaneous ad- vance along the whole austrian front up to the carpathians. the russians had halted on the san after their defeat of the austrians, and were in the process of transferring troops north to form a new front south of warsaw. this re-grouping was carried out in safety behind the vistula, only cavalry being left to oppose the german advance west of the river. by the middle kastern european front campaigns of oct. the german ix. army was near warsaw, but the austrian advance had been held up on the san. the russians new counter-attacked all along the line. in the south they drove the austrians back to the dunajec, in the centre they compelled the german ix. army to fall back, and in the north the newly- constituted x. army crossed the frontiers of east prussia. the intention of the russian commander-in-chief was now to invade silesia with his v., iv. and ix. armies, in that order from the north. his right flank was to be protected by the x. army in the east of east prussia and by the i. and ii. armies north and west of warsaw, his left flank by the advance of the iii. and vii. armies in galicia. but the germans had thor- oughly broken up communications in south-west poland during their retreat, and the russian advance was slow and halting. their more nimble opponents once again used the superior mobility given them by their highly developed network of railways to launch a telling counterstroke. a german eastern front command was constituted under hindenburg and luden- dorff, and the ix. army, now under mackensen, was withdrawn from south-west poland and concentrated between posen and toran. it advanced on nov. 11, with its left flank on the vistula, against the right flank and rear of the russian main armies. the russian 1]. and ii. armies were severely mauled, and the latter was by nov. 17 in a critical situation, almost completely surrounded at l6dz. it was saved by a skilful counterstroke of plehve’s v. army; and the germans in their turn were in danger of envelopment and disaster. thanks to rennen- kampf’s failure to act with energy they extricated themselves with credit. four corps from the western front released by the conclusion of the ypres battle now joined mackensen, and en- abled him again to advance and to capture lowicz and ledz by dec. 12. in the south heavy fighting had taken place east of cracow with no decisive result (see l6pz-cracow). il. the austro-german advance into russia january—a pril.—the 1914 campaign had ended in stalemate both in east and west. the german plan of a swift overthrow of france, to be followed by an unhurried reckoning with russia, had miscarried. and her austrian allies were already penlously near to breaking under the strain. from now onwards german formations had to be interwoven into the austrian battle line to stiffen its uncertain fabric. on the other side, the weaknesses already evident in the russian army were increased by the de- ficiencies in munitions, especially rifles and shell, which now began to be seriously felt. even the severity of winter gave little check to the fighting. in the centre the front remained stable but furious battles on either flank marked the opening months of 1915. on the russian side, the grand duke had realised that he must secure his flanks solidly before any further attempt to advance in the salient. the problem was on which flank to make the main effort; on this point russian strategists were divided. the majority were for making an end of austria; others urged, very reasonably, that the occupation of east prussia would do more than any- thing else to solve russia’s strategical problem. in the end both were attempted and neither aim was accomplished. conflicting german plans.—on the german side, there now became evident a fundamental difference of opinion between falkenhayn at supreme command and ludendorff, the guiding brain of the campaign on the eastern front. the latter aimed at nothing less than decisive manoeuvre on the largest scale against the russian armies, and now urged that all available resources should be put into a great effort from both flanks, which was to finish the eastern campaign once for all. fal- kenhayn judged the distance too great and thecommunications too sparse for manoeuvre on such a scale. he would admit only the limited offensive which sought tactical success; he hoped by a serics of such successes to wear out the resisting powers of the russian army. on the southern flank, battle raged all along the carpathians from jan. to mid-april. the russians sought to secure the crest of the mountains and to debouch on to the plains below. eastern front campaigns scale, i: 5,000,000 english miles 0 10 20 40 60 80 1090 kilometres ne ny sanne gses sen san eee eee 0 20 40 60 80 !00 !20 140 160 180200 reference approximate positions germans & austrians. . august 20° /9/4 (strategical deployment) russians . approximate /ine may /% 1915. a ee | i » = aug.15* 1915. » sept. 15% 19/5 oe hd) (ena of russian retreat ) approximate line nov.30°\" (9/6 main railways : co marshes su stun sas + wtoctawek »{ viotstavsk ) czestochowe (chensty hv} dy pillar