From 1894 to 1918, Rwanda, along with Burundi, was part of German East Africa. After Belgium became the administering authority under the mandates system of the League of Nations, Rwanda and Burundi formed a single administrative entity; they continued to be jointly administered as the Territory of Ruanda-Urundi until the end of the Belgian trusteeship in 1962. By then, however, the two states had evolved radically different political systems, with Rwanda having declared itself a republic in January 1961 and forced its monarch (mwami), Kigeri, into exile. Burundi, on the other hand, retained the formal trappings of a constitutional monarchy until 1966.
The Rwanda revolution was rooted partly in a traditional system of stratification based on an all-embracing "premise of inequality" and partly in a colonial heritage that greatly increased the oppressiveness of the few over the many. Tutsi hegemony was unquestionably more burdensome under Belgian rule than at any time prior to European colonization. By the end of World War II, a growing number of colonial civil servants and missionaries had come to recognize the legitimacy of Hutu claims against the ruling Tutsi minority. The proclamation of the republic a year and a half before the country acceded to independence testifies to the substantial support extended by the trusteeship authorities to the revolution.
What began as a peasant revolt in November 1959 eventually transformed itself into an organized political movement aimed at the overthrow of the monarchy and the vesting of full political power in Hutu hands. Under the leadership of Grégoire Kayibanda, Rwanda's first president, the Party for Hutu Emancipation (Parti du Mouvement de l'Emancipation du Peuple Hutu) emerged as the spearhead of the revolution. Communal elections were held in 1960, resulting in a massive transfer of power to Hutu elements at the local level. And in the wake of the coup (January 1961) in Gitarama in central Rwanda, which was carried off with the tacit approval of the Belgian authorities, an all-Hutu provisional government came into being. Therefore, by the time that the republic was proclaimed in July 1962, the revolution had already run its course. Thousands of Tutsi began fleeing Rwanda, and by early 1964--following a failed Tutsi raid from Burundi--at least 150,000 were in neighboring countries.