sentences:  The preferred route was via the Zambezi and Lake Nyasa (Lake Malawi) but Harry Johnston, British Commissioner in Nyasaland who had acted for Rhodes by sending Sharpe on his failed mission to Msiri, advised that military action he was taking against slave traders made that route unsafe.Instead they crossed German East Africa from Zanzibar, marching 1050 km during the dry season to Lake Tanganyika through country with potentially hostile tribes and slave traders.They crossed the lake by boat, then marched 550 km to Bunkeya as extreme heat and humidity indicated the build-up to the rainy season which then brought chilling rain, mosquitoes and insanitary conditions.