Security for the Rumanian forces could not, however, be found short of the Sereth, which would give them a straight line with the Russian frontier protected by the impassable delta of the Danube on their left, and a flank in the Carpathians on their right; and from the fall of Bukarest to the end of December Averescu the Rumanian commander, and Presan his chief of staff, retreated to this line fighting rearguard battles on the way. The most stubborn of these was a four days' conflict at Rimnic Sarat in the centre on 22-26 December, after which Mackensen entered the town on the 27th. Sakharov conformed to this retreat in the Dobrudja; on 4 January Macin, the last place east and south of the Danube, was evacuated, and on the 5th Braila on the opposite bank south of the Sereth and Danube confluence. On the 23rd the Bulgarians, taking advantage of the unprecedented frost, crossed the marshes at Tulcea, but were annihilated by the Rumanians on the northern bank, and remained content for the rest with the defensive. The same wintry conditions put an end to fighting at the other extremity of the line in the Carpathian passes, but in the centre Mackensen seized Focsani on the 8th and occupied the bank of the Sereth. That line had originally been fortified against the Russians, and it faced in the wrong direction; but the position was strong, and when on the 19th Mackensen sought to force it he was repulsed in a costly encounter. Russian reinforcements which might have saved Wallachia came in time to protect Moldavia; and the war-worn Rumanian army was retired to refit, the defence of the Sereth being left to the Russians. The Germans made the most of their booty in Wallachia, which suffered the fate of Belgium and of Serbia; though the stores of grain had been burnt and the Rumanian oil-wells put out of action for many months. In one respect Rumania was less fortunate than the other little nations: in his fanatical hatred of Russia, Carp rejoiced in her ally's defeat--albeit that country was his own--and Marghiloman remained in Bukarest to curry favour with its conquerors, and ultimately to become for a brief and discreditable period the Premier whom the Germans imposed on Rumania after the Treaty of Bukarest. Meanwhile the patriotic parties rallied round the ministry at Jassy and formed a Coalition Government.

The defence of Rumania now seemed to occupy all the energy Russia could spare from her domestic preoccupations. In January there was a sound strategical effort to divert German attention from the south by a counter-offensive from Riga, and an advance of some four miles was made to Kalnzem. But the Germans soon recovered most of the ground; and elsewhere the front was quiescent. There was no repetition of the great blow at Erzerum of January 1916, and in Persia Baratov's small but adventurous force was driven back by the Turks from Khanikin to Hamadan, and the resistance to Turco-Teutonic invasion and intrigue was left more and more to British effort. Co-operation seemed impossible to synchronize in the East; one partner retreated whenever the other advanced. While therefore the Russians halted in Asia Minor and withdrew in Persia, Sir Stanley Maude was gathering his forces for a spring on Baghdad. Gorringe had already in May 1916 advanced some way up the right bank of the Tigris towards Kut; but summer forbade active operations, and Maude had been duly impressed by the force which previous experiences in Mesopotamia had given to the adage about more haste and less speed. The autumn was spent in careful study and preparation, which would preclude a repetition of the retreat from Ctesiphon and the fall of Kut (see Map, p. 177).

By 12 December he was ready to attack. The Turks still held the Sanna-i-Yat positions on the left bank of the Tigris, but on the right they had been pushed back to a line running across the angle from the Tigris at Magasis towards its southern tributary the Shatt-el-Hai. The Turks under their German taskmasters had not been idle, and this angle, as well as the extension of the Turkish line along the Shatt-el-Hai and their secondary defences on the right bank of the Tigris above Kut, had been well protected by trenches and wire entanglements. The breaking down of these obstacles required stubborn fighting as well as skilful tactics, but the only alternative was to penetrate the Sanna-i-Yat positions and they had proved impregnable in the spring. A serious attempt had, however, to be made at Sanna-i-Yat in order to detain there a serious Turkish force; and while Marshall pushed his way through on the right bank, Cobbe was kept hammering on the left. On the 13th crossings of the Shatt-el-Hai were effected at Atab and Basrugiyeh some eight miles from Kut, and Marshall advanced on both banks to Kalah-Hadji-Fahan. On the 18th he reached a point on the Tigris just below Kut in the Khadairi bend. Rain and floods then impeded our advance for a month, but the Khadairi bend was gradually cleared of the Turks, and most of their positions in the angle of the Tigris and Shatt-el-Hai were taken. On 10 February Marshall pushed on beyond the Shatt-el-Hai, reached the right bank of the Tigris above the Shumran bend, and by the 16th forced the Turks in the Dahra bend across the river.

The Turks had now been driven off the right bank below, in front of, and far above Kut, but they held the left bank as far down as Sanna-i-Yat, and Maude's task was to find a way across. He chose the Shumran bend, but diverted the attention of the Turks by thrusting at Sanna-i-Yat from 17 to 22 February. On the 22nd he also made feints to cross at Magasis and Kut, but on the 23rd the real attack was made at Shumran. Troops were ferried across and a bridge built before evening, and on the 24th the Turks were driven back on to their lines of communication between Baghdad and Kut. Meanwhile Cobbe had forced six enemy lines at Sanna-i-Yat and then found the remainder deserted. The Turks were in full retreat towards Baghdad, and Cobbe entered Kut unopposed. The pursuit was taken up by Marshall, who reached Azizieh in four days. There he halted till 5 March to prepare for his final advance. On the 6th he passed deserted trenches at Ctesiphon, and on the 7th reached the Diala. For two days the Turks disputed the passage, but a force, transported to the right bank of the Tigris, enfiladed their position on the Diala and captured their trenches at Shawa Khan on the 9th. Our forces on both sides of the river entered Baghdad on the 11th, thus concluding a model campaign which reflected glory alike on the British and Indian troops engaged and on their commanders, and raised British prestige in the East higher than it had been before the fall of Kut.

The work of our armies in Egypt was less sensational, but it was making solid progress and laying firm foundations during the autumn of 1916. The Grand Sherif of Mecca was proclaimed king of the Hedjaz, and he was a thorn in the side of the Turks. Their defeat at Romani had been followed by the steady construction of a railway eastward across the desert from Kantara, and on 20 December El Arish was captured, while on the 23rd the Turks who had fled south-east to Magdhaba were there surrounded and forced to surrender. The success was repeated at Rafa on the Palestine frontier a fortnight later, and presently the whole Sinai peninsula was cleared of the enemy forces (see Map, p. 352). Early in February a final blow was struck on the western frontiers of Egypt at the Senussi, and Egypt was converted from an enemy objective into a fruitful basis of operations against the Turkish Empire. Whatever might be said for frontal attacks in the west of Europe, ways round were proved to be the shortest in the East, and the failure of the direct blow at Turkey's heart in the Dardanelles was redeemed by success along the circuitous routes through Egypt and Mesopotamia.

Among the other forgotten achievements of the first two and a half years of the war was the completion, chiefly by British arms, of the establishment in the African continent of Entente and mainly British supremacy. For even before the Turks had been driven from the frontiers of Egypt the Germans had been expelled from all the important parts of East Africa. The progress had been slow and not very creditable to our earlier efforts, which failed through an underestimate of the German strength, and particularly of the skill and resource of the German commander Von Lettow-Vorbeck. But it was sound as well as inevitable strategy to make sure of what we had by suppressing rebellion in the South African Union and then securing its frontiers by the conquest of its German neighbour before proceeding to concentrate forces for an offensive against an isolated German stronghold which could not threaten any essential interest nor affect the main struggle for victory in the war. The case against divergent operations was strongest of all against the East African campaign; and it would have been criminal folly for the sake of amour propre or imperial expansion to diminish our safeguards against a German victory in the West, or weaken the defence of our threatened communications with Egypt and India. Von Lettow-Vorbeck had forces enough to hold his own, but he never even attempted the conquest of British East Africa or the Belgian Congo, and the most nervous anticipation could not picture him as a serious danger to other dominions.

He was therefore left very much to himself until the South African Union, having set its own house in order and secured its frontiers by expelling German rule from the southern part of the continent, was able to lend its military power and its generalship to the task of reducing the Germans in East Africa. It was formidable enough, not so much from the opposition of man as because of the obstacles nature placed in the way. A tropical climate, torrential rains which played havoc with transport, the tzetze-fly which slew beasts of burden in hundreds of thousands, impenetrable forests, impassable swamps, immense mountain masses, and an area almost as large as Central Europe, provided a problem as vast as that of the great Boer War, and more difficult of solution but for the fact that Von Lettow-Vorbeck's forces could not be compared with those of our past antagonists and present allies. Still they were far more dangerous than any we had encountered in our normal wars against native races; for they had been trained by German officers, experts with machine guns and the other scientific equipment of civilized conflict; and three ships at least had eluded the blockade and relieved Von Lettow-Vorbeck's most pressing need of munitions; and he had selected his coloured troops from the hardiest and most bellicose of the native tribes. With their help he had kept the German colony intact until 1916, and even held at Taveta an angle of British East Africa.

Smith-Dorrien had been selected for the command in the autumn of 1915, but ill-health prevented him from taking it up, and in February 1916 General Smuts arrived at Mombasa to conduct the campaign. Experience had made us shy of enforced landings from the sea; and rejecting the idea of seizing as bases Tanga or Dar-es-Salaam, which would have given him shorter lines of communication with the Cape, Smuts adopted the more circuitous route by the railway from Mombasa, with the design of forcing the gap below Kilimanjaro and driving the Germans southwards, while British and Belgian subsidiary forces impinged upon the enemy's flank from the Lakes, the Congo State, and Nyasa in the west. His advance began on 5 March and Taveta was occupied on the 10th. A frontal attack on the pass between Kilimanjaro and the Pare mountains savoured rather of British than Boer methods, and Smuts preferred to send Van Deventer round the north of Kilimanjaro to turn the German position from Longido and cut off their escape. Van Deventer was successful, and at Moschi blocked the Germans' retreat westwards; they managed, however, to slip away south-eastwards by Lake Jipe, but the Kilimanjaro massif had been cleared, and Smuts established his headquarters at Moschi. His force was now arranged in three divisions, the first under Hoskins, the second under Van Deventer, and the third under Brits; the first consisted of British and Indian troops, the two others of South African. The plan was to strike with the second division from Moschi towards Kondoa Irangi and thence at the German central railway, while the first and third cleared the Pare and Usambara mountains and the coast, and then marched on Handeni and threatened the central railway on a parallel line to Van Deventer's attack. Van Deventer's second division marched with almost incredible speed. He started from Aruscha on 1 April, and by the 19th had driven the Germans from Kondoa Irangi, more than a hundred miles away. In May and June the other divisions cleared the Pave and Usambara mountains, reached Handeni and Kangata, and with naval assistance occupied Tanga, Pangani, Sadani Bay, and Bagamoyo in July and August almost without opposition. Von Lettow-Vorbeck had transferred the bulk of his troops south and then westwards up the central railway to bar Van Deventer's progress; and in the process he had been forced to abandon the north-eastern quarter of the colony. No small part of the north-western province of Ruanda had been lost as well: the Belgians had occupied Kigali and the British had driven the Germans from their shore of Lake Victoria Nyanza.

The rapidity and divergence of these attacks, which were admirably timed, distracted Von Lettow-Vorbeck's strategy, and in spite of his interior lines he was unable to offer successful resistance. No sooner did he send troops to bar Smuts' advance from Kangata into the Nguru hills than Van Deventer struck west, south, and south-east from Kondoa Irangi. To the west he took Singida, thus getting behind the Germans on Lake Tanganyika; to the south and south-east he got astride the central railway by 14 July and pushed down it eastwards to Kilossa, which he reached on 22 August. He was now almost due south the Nguru hills, whence Smuts, attacking from the north, had driven the Germans before the middle of August. This converging advance made Mrogoro the only line of retreat, and Smuts planned a complicated outflanking movement to intercept it. They escaped by a track unknown to our forces on the 26th, and prepared to stand south of the central railway in the Ulunguru hills. Smuts was too quick for them, but they repelled a badly-timed attack at Kissaki on 6 September. Their retreat had, however, made the coast untenable: on 3 September the capital Dar-es-Salaam surrendered, and all the remaining ports before the end of the month. Van Deventer, too, had pressed south to the Ruaha on the 10th, the Belgians occupied Tabora on the 19th, and General Northey, advancing from Nyasa in the south-west, had reached Iringa before the end of August, while some Portuguese troops crossed the Rovuma river, the frontier between German East Africa and Mozambique, and made a pretence of marching north. By the end of September the great German colony had been conquered save for the unhealthy south-eastern corner, where only the Mahenge plateau provided a decent habitation for white troops.