In the 1980s, a group of 500 Banyarwanda refugees in Uganda, led by Fred Rwigyema, fought with the rebel National Resistance Army (NRA) in the Ugandan Bush War, which saw Yoweri Museveni overthrow Milton Obote. These soldiers remained in the Ugandan army following Museveni's inauguration as Ugandan president, but simultaneously began planning an invasion of Rwanda through a covert network within the army's ranks. In 1990, the soldiers broke ranks and launched an invasion of northern Rwanda as the Rwandan Patriotic Front (RPF), initiating the Rwandan Civil War; neither side was able to gain a decisive advantage, and in 1993 the Rwandan government and the RPF signed a cease-fire. This ended on 6 April 1994 when President Habyarimana's plane was shot down near Kigali Airport, killing him. The shooting down of the plane served as the catalyst for the Rwandan genocide, which began within a few hours. Over the course of approximately 100 days, between 500,000 and 1,000,000 Tutsi and politically moderate Hutu were killed in well-planned attacks on the orders of the interim government. Many Twa were also killed, despite not being directly targeted. The RPF restarted their offensive, and took control of the country methodically, gaining control of the whole country by mid-July.