When in January, 1917, I relinquished the command to my successor,
General Hoskins, we were across the Rufiji River in the southeast, and
in the great valley formed by the principal tributaries, the Ulanga and
Ruhuje rivers in the west; but the rainy season which set in shortly
afterward stopped all advance until the following June.

[Sidenote: Enemy's forces evacuate German East Africa.]

Five months later our advance was resumed, and by the beginning of
December, 1917, the last remnants of the enemy's forces had evacuated
German East Africa across the Rovuma, while our forces were operating
against the enemy bands far south in Portuguese territory, as I have
already stated.

[Sidenote: Development of tropical Africa retarded by diseases.]

In economic value this region ranks very high among the tropical
countries of the African continent, and probably no part of all Africa
has a climate or soil more suitable for the production on an immense
scale of copra, cocoanuts, coffee, sugar, sisal, rubber, cotton, and
other tropical products, or of such semi-tropical products as maize and
millet. In common with the rest of tropical Africa, its full development
is still retarded by the undefeated animal and human diseases,
especially malaria. But the time is not far distant when science will
have overcome these drawbacks, and when Central and East Africa will
have become one of the most productive and valuable parts of the
tropics. But until science solves the problems of tropical disease, East
and Central Africa must not be looked upon as an area for white
colonization. Perhaps they will never be a white man's country in any
real sense. In those huge territories the white man's task will probably