When in the latter part of May the rains subsided, the advance against the enemy was once more resumed.  In order to create the maximum difficulties for our advance, the enemy chose as his line of retreat the great block of mountains which I have referred to as forming the eastern buttress of the great central plateau.  For the next three and a half months our forward movement continued with only one short pause until by the middle of September we had reached the great valleys of the Rufiji and the Great Rwaha in the far south, and across the Rwaha we could link up with General Northey at Iringa in the southwest.

[Sidenote:  Difficulties of transport and supply in advance.]

[Sidenote:  Poisonous insects and tropical diseases.]

[Sidenote:  The campaign a story of human endurance.]

It is impossible for those unacquainted with German East Africa to realize the physical, transport, and supply difficulties of an advance over this magnificent, but mountainous, country, with a great rainfall and wide, unbridged rivers in the regions of the mountains, and insufficient surface water on the plains for the needs of an army; with magnificent primeval forest everywhere, pathless, trackless, except for the spoor of the elephant or the narrow footpaths of the natives.  The malaria mosquito is everywhere except on the higher plateaus; everywhere the belts are infested with the deadly tsetse fly, which makes an end of all animal transport; and almost everywhere the ground is rich black or red cotton soil, which any transport converts into mud in the rain or dust in the drought.  Everywhere the fierce heat of equatorial Africa, accompanied by a wild luxuriance of parasitic life, breed tropical diseases in the unacclimatized whites.  These conditions make life for the white man in that country sufficiently trying.  If in addition he has to perform hard work and make long marches on short rations, the trial becomes very severe; if, above all, huge masses of men and material have to be moved over hundreds of miles in a great military expedition against a mobile and alert foe, then the strain becomes almost unendurable.  And the chapter of accidents in this region of the unknown!  Unseasonable rains cut off expeditions for weeks from their supply bases.  Animals died by the thousand—­after passing through an unknown fly-belt.  Mechanical transport got bogged in the marshes, held up by bridges washed away, or mountain passes obstructed by sudden floods.  And the gallant boys, marching far ahead under the pitiless African sun, with the fever raging in their blood, pressed ever on after the retreating enemy, often on reduced rations, and without any of the small comforts which in this climate are real necessities.  In the story of human endurance this campaign deserves a very special place, and the heroes who went through it uncomplainingly, doggedly, are entitled to all recognition and reverence.  Their commander-in-chief will remain eternally proud of them.