During the First World War (1914–18), an expanded "Force Publique" served against German colonial forces in the Camerouns and German East Africa (Tanzania, Rwanda, Burundi), as part of the East African Campaign. The "Force Publique" performed well on the battlefield, winning the respect of their British and Portuguese allies, as well as that of their German opponents. From 1916 onwards, the "Force Publique" grew to reach a strength of three mobile "Groupes" (brigades), Kivu, Ruzizi, and Tanganyika, comprising a total of 15 battalions, from the static garrison and police force of 1914. However, it did take until late 1915 for the "Force Publique" to finish preparations for a large scale offensive on the German colony of German East Africa. The allied powers, the British Empire and Belgium, launched a coordinated attack on the German colony; by 1916 the Belgian commander of the "Force Publique", Lieutenant-General Charles Tombeur, had assembled an army of 15,000 men supported by local bearers and advanced to Kigali. Kigali was taken by 6 May 1916. The German army stationed in Urundi was forced to retreat by the numerical superiority of the Belgian army, and by 17 June 1916, Ruanda-Urundi was occupied. The "Force Publique" and the British Lake Force then started a thrust to capture Tabora, an administrative centre of central German East Africa. The army went on to take Tabora on 19 September after heavy fighting. At the time of the Battle of Tabora in September 1916, about 25,000 men were under arms; during the war their actions were supported by more than 260,000 local bearers. In 1916, Charles Tombeur was made Military Governor of the Belgian Occupied East African Territories. After the Mahenge Offensive and the capture of Mahenge in 1917, the Belgian Congolese army controlled roughly one-third of German East Africa.