 Belgium took control of Rwanda and Burundi during World War I, forming the mandate of Ruanda-Urundi.Kigali remained the seat of colonial administration for Rwanda but Ruanda-Urundi's capital was at Usumbura (now Bujumbura) in Burundi and Kigali remained a small city with a population of just 6,000 at the time of independence.Kigali grew slowly during the following decades.