administrative reforms; these included ubuhake, in which Tutsi patrons ceded cattle, and therefore privileged status, to Hutu or Tutsi clients in exchange for economic and personal service, and uburetwa, a corvée system in which Hutu were forced to work for Tutsi chiefs. Rwabugiri's changes caused a rift to grow between the Hutu and Tutsi populations. The Twa were better off than in pre-Kingdom days, with some becoming dancers in the royal court, but their numbers continued to decline.
The Berlin Conference of 1884 assigned the territory to Germany as part of German East Africa, marking the beginning of the colonial era. The explorer Gustav Adolf von Götzen was the first European to significantly explore the country in 1894; he crossed from the south-east to Lake Kivu and met the king. The Germans did not significantly alter the social structure of the country, but exerted influence by supporting the king and the existing hierarchy and delegating power to local chiefs. Belgian forces took control of Rwanda and Burundi during World War I, beginning a period of more direct colonial rule. Belgium simplified and centralised the power structure, and introduced large-scale projects in education, health, public works, and agricultural supervision, including new crops and improved agricultural techniques to try to reduce the incidence of famine. Both the Germans and the Belgians promoted Tutsi supremacy, considering the Hutu and Tutsi different races. In 1935, Belgium introduced identity cards labelling each individual as either Tutsi, Hutu, Twa or Naturalised. While it had previously been possible for particularly wealthy Hutu to become honorary Tutsi, the identity cards prevented any further movement between the classes.
Belgium continued to rule Rwanda as a UN Trust Territory after World War II, with a mandate to oversee independence. Tension escalated between the Tutsi, who favoured early independence, and the Hutu emancipation movement,
