What is the Rwandan Genocide?

According to Wikipedia,

"The Rwandan Genocide was the 1994 mass killing of hundreds of thousands of Rwanda's Tutsis and Hutu political moderates by Hutus under the Hutu Power ideology. Over the course of approximately 100 days, from the assassination of Juvenal Habyarimana on April 6 through mid-July, at least 500,000 people were killed. Most estimates indicate a death toll between 800,000 and 1,000,000, which could be as high as 20% of the total population.

The genocide has its roots in the Hutu-Tutsi ethnic divide and related sporadic violence, which had resulted in a large number of Tutsi refugees in the nations around Rwanda by 1990. In that year, the Rwandan Patriotic Front (RPF), a rebel group composed mostly of Tutsi refugees, invaded. The Rwandan Civil War, fought between the Hutu regime, with support from Francophone nations of Africa and France itself, and the RPF, with support from Uganda, vastly increased the ethnic tensions in the country and led to the rise of Hutu Power, an ideology that stressed that the Tutsi intended to enslave Hutus and thus must be resisted at all costs. Despite ongoing ethnic tension, including the displacement of large numbers of Hutu in the north by the rebels and periodic localized ethnic cleansing of Tutsi to the south, pressure on the government of Juvenal Habyarimana led to a cease-fire in 1993 and the preliminary implementation of the Arusha Accords.

A genocidal plan had existed since 1957, when the Hutu Emancipation Movement called the Parmehutu published the "Bahutu" Manifesto, in which it alleged a monopoly of power held by the Tutsi minority. In the 1960s, these denunciations led to the overthrowing of the monarchy and the establishment of the Republic headed by Gregoire Kayibanda. This was a regime which persecuted the Tutsi, who in many cases were forced to flee. The persecution also went on under the regime of Juvenal Habyarimana who had seized power in 1973 and promised progress and reconciliation.

The assassination of Habyarimana in April 1994 was the proximate cause of the mass killings of Tutsis and pro-peace Hutus. It was carried out primarily by two Hutu militias associated with political parties: the Interahamwe and the Impuzamugambi. The genocide was directed by a Hutu Power group known as the Akazu. The killing also marked the end of the peace agreement meant to end the war and the Tutsi RPF restarted their offensive, eventually defeating the army and seizing control of the country."

For more details, the link to the full Wikipedia article is on the right side of the page under "For Further Reading"