In 1964, following an incursion from Burundi, which continued to be controlled by its Tutsi aristocracy, many Tutsis were killed in Rwanda, and numerous others left the country. In early 1973 there was renewed fighting between Hutu and Tutsi groups, and some 600 Tutsis fled to Uganda.
On July 5, 1973, a military group toppled President Kayibanda without violence and installed Major General Juvénal Habyarimana, a moderate Hutu who was commander of the national guard. In 1978 a new constitution was ratified and Habyarimana was elected president. He was reelected in 1983 and 1988. In 1988 over 50,000 refugees fled into Rwanda from Burundi.
Two years later Rwanda was invaded from Uganda by forces of the Rwandan Patriotic Front (RPF), consisting mainly of Tutsi refugees. They were repulsed, but Habyarimana agreed to a new multiparty constitution, promulgated in 1991. In early 1993, after Habyarimana signed a power-sharing agreement, Hutu violence broke out in the capital; subsequently, RPF forces launched a major offensive, making substantial inroads. A new accord was signed in August, and a UN peacekeeping mission was established. However, when Habyarimana and Burundi's president were killed in a suspicious plane crash in April, 1994, civil strife erupted on a massive scale. Rwandan soldiers and Hutu gangs slaughtered an estimated 500,000-1 million people, mostly Tutsis and moderate Hutus. The RPF resumed fighting and won control of the country, but over 2 million Rwandans, nearly all Hutus, fled the country.
In 1995, a UN-appointed tribunal, based in Tanzania, began indicting and trying a number of higher-ranking people for genocide in the Hutu-Tutsi atrocities; however, the whereabouts of many suspects were unknown. A number of former senior Rwandan government and military officials were convicted of organizing the genocide or having participated in it. Many more individuals were tried and convicted in Rwandan courts over the next two decades, with nearly 2 million suspects, most of whom were accused of looting and other property crimes, tried in semitraditional community courts. Over a million Hutu refugees flooded back into the country in 1996; by 1997, there was a growing war between the Rwandan army and Hutu guerrilla bands.