At the end of the First World War, German East Africa was divided into a British mandate (Tanganyika) and a Belgian mandate (Ruanda-Urundi). The boundary between the two mandates was initially delimited in 1924, and the frontier applying to modern-day Rwanda and Tanzania was adjusted in greater detail by the colonial powers in 1934. The boundary follows the thalweg of the Kagera River in the north and south for a total of 127 kilometers. The middle reaches of the frontier connect a series of boundary markers through swampy lowlands for 98 kilometers. The total length of the Rwanda–Tanzania frontier, from the tripoint with Uganda in the north to the tripoint with Burundi in the south is 225 kilometers.