On this day in 1994, Rwandan armed forces kill 10 Belgian peacekeeping officers in a successful effort to discourage international intervention in the genocide that had begun only hours earlier. In approximately three months, the Hutu extremists who controlled Rwanda brutally murdered an estimated 500,000 to 1 million innocent civilian Tutsis and moderate Hutus in the worst episode of ethnic genocide since World War II. The immediate roots of the 1994 genocide dated back to the early 1990s, when President Juvenal Habyarimana, a Hutu, began using anti-Tutsi rhetoric to consolidate his power among the Hutus. Beginning in October 1990, there were several massacres of hundreds of Tutsis. Although the two ethnic groups were very similar, sharing the same language and culture for centuries, the law required registration based on ethnicity. The government and army began to assemble the Interahamwe (meaning "those who attack together") and prepared for the elimination of the Tutsis by arming Hutus with guns and machetes. In January 1994, the United Nations forces in Rwanda warned that larger massacres were imminent.