As a lieutenant-colonel in February, 1914, he was appointed commander of the forces in German East Africa, with a dozen companies of askari troops. In August, 1914, effectively isolated from outside command, von Lettow-Vorbeck launched a series of effective raids against the British railway in Kenya, attempted to conquer Mombasa, fought off a British amphibious attack on Tanga and finally captured large amounts of arms and ammunitions to supply his troops. von Lettow-Vorbeck managed to salvage the guns from the destroyed ship Konigsberg, and was able to use these along with the rigours of the terrain to hold off the offensive of Gen. Jan Christiaan Smuts in March, 1916. He remained continually on the offensive, gradually working south, and in December 1917 invaded Mozambique, and advanced as far south as Quelimane (July 1918), invaded Rhodesia in the fall and captured Kasama, Zambia on 13 November 1918. He officially surrendered to the British, having never been defeated, on 23 November 1918, at Mbaala, Zambia, and arranged for the re-patriation of German soldiers and prisoners of war before his departure for Germany in January, 1919. von Lettow-Vorbeck never had more than approximately 12,000 troops at his disposal, but tied down as many as ten to twenty times that number of Allied troops.