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