Complex sentence: The Tutsi-led Rwandan Patriotic Front launched a civil war in 1990, which was followed by the 1994 genocide, in which Hutu extremists killed an estimated 500,000 to 1 million Tutsi and moderate Hutu.
Split into simpler sentences: The Tutsi-led Rwandan Patriotic Front launched a civil war in 1990. Social tensions erupted in the 1994 genocide, in which Hutu extremists killed an estimated 500,000 to 1 million Tutsi and moderate Hutu.