 Kutevera kutanga kweHondo Yenyika I uye kupinda kweGermany muBelgium, Tombeur akava mutungamiri wemauto eBelgian colonial pamuganhu neGerman East Africa. Akatungamira kurongwazve kwe Force Publique uye, muna Kubvumbi 1916, akatungamira simba reBelgium kupinda muRwanda sechikamu cheBritish-inotungamirwa East Africa Campaign. Pakazosvika June 1916, Rwanda yose yakanga yadonha uye Burundi yakatorwa nokukurumidza pashure pacho. Tombeur akaitwa gavhuna wemauto weBelgian Occupied East African Territories inosanganisira ramangwana reBelgian mandate reRwanda-Urundi. Pasina nguva refu boka racho rakanga raenda kunhare yemauto eGermany kuTabora muTanzania yemazuva ano. Pashure pokurwa kwenguva refu, Tombeur akapinda mutaundi musi wa 20 Gunyana 1916. Tombeur akadanwa kuEurope mukupera kwa1916 uye akatsiviwa semutungamiri muEast Africa naArmand Huyghé. Mukutanga kwa1917, akasimudzirwa pachinzvimbo cheVice-Governor-General, chinzvimbo chechipiri chepamusoro muCongo. Akashanda segweta reKatanga kubva muna 1918 kusvika muna 1920. 