When World War I broke out in August 1914, he ignored orders from Berlin and his governor, and seized the initiative to attack the British city of Taveta.

After repulsing General Aitken's attack on Tanga and Longido in November 1914, he gathered his forces and supplies and moved to harass the British rail communications in East Africa, helping the German war effort by tying down as much British troops possible in East Africa.

In 1916, Lettow-Vorbeck had managed to successfully harass the British Central Railway to Uganda without being forced in an engagement, which he would certainly lose being hopelessly outnumbered.

After leaving Dar es Salaam to the British, he withdrew to a position in the easily defended Uluguru Mountains.

German Field Artillery and 4.1 inch (100 mm) guns, salvaged from the SMS Koenigsberg, blasted the South African formations.