During World War I the colonial forces in the Belgian Congo provided a crucial contribution to the Allied war effort against Germany. The Force Publique was reorganized and enlarged to meet the new dangers of the war and early on units were sent to assist the French in the conquest of the the German colony of Kamerun (Cameroon). In command was General Baron Charles Tombeur, who was a very effective commander but who did not get along well with his British opposites. When the time came for the major campaign against German East Africa and the inland city of Tabora where the Germans had moved their capital, the British and Belgians had to deal with their differences and work together. That, at least was the idea, it did not quite work out that way. The British had already decided German East Africa would belong to their empire after the war and they were already annoyed that a country as small as Belgium ruled so much of central Africa.
However, this rivalry ended up not harming the Allies much and may have contributed to success by making the capture of Tabora a competition. The Belgians wanted to take it to show what they could do, prove themselves and win some victories on German territory since the Germans had conquered most of their homeland. The British wanted to take Tabora and advance as far west as quickly as possible to keep the Belgians from claiming any of "their" German territory once the war was over. It was a race! But of course there were also the Germans to deal with. Captain Max Wintgens oversaw the blocking of the Belgian offensive while General Kurt Wahle held overall command of the western region of the German colony at Tabora with the colonial governor. The British raced ahead and were caught by natural conditions and the Germans overreaching and were forced to slow down. General Tombeur, on the other hand, made slower but steadier progress with the Belgian army.
It was a massive undertaking, the Force Publique having more artillery and machine guns than most colonial forces and it took 260,000 carriers to keep the troops supplied. But they came on, in two columns, south and north, led by Colonel Molitor and Lt. Colonel F.V. Olsen who was actually a Danish officer in the employ of the Force Publique. They started on 18 April 1916 and captured Kigali on 6 May. Pushing into the rich provinces of Rwanda-Burundi, the Germans put up a stubborn fight by the Belgian forces pushed them back, moving slowly, methodically with lots of fire support. These provinces were taken and General Tombeur moved against the city of Tabora which General Wahle had taken care to defend. On 19 September, after ten days of heavy fighting, the Germans gave up and abandoned Tabora and the Belgian Congo army marched proudly into the capital. They had beaten the British to the prize! The Germans later claimed that the Belgians mistreated their civilians in retaliation for how their homeland was treated. This was not true naturally, the Belgian forces behaved very correctly, but the angered Germans used this as an excuse to arrest a corresponding number of Belgians and send them to concentration camps in Germany.
The British commander, General Smuts (actually a Dutch Afrikaner) ordered the Belgians to halt and return home so they would not get too comfortable in territory the British claimed. However, King George V sent congratulations to King Albert I and sent a knighthood to General Tombeur, congratulating him on his cooperation with the British army, even though both sides did not really cooperate with each other. King Albert I said that the colonial army had upheld the honor of Belgian arms on African soil by this considerable victory. It seemed to many that the war was over for the Belgian Congo after that, but it was not completely even though the only German forces left moved pretty far away. When a rogue German unit broke away to go off on their own and fight their own war they made things pretty hot for the British, who had their focus on the main German army elsewhere, and the Belgian army had to be called in again to deal with this threat which they successfully did.