The revolution caused at least 336,000 Tutsi to flee to neighbouring countries, where they lived as refugees. Although the exiles agitated for an immediate return to Rwanda, they were split between those seeking negotiation and those wishing to overthrow the new regime. Some exiles formed armed groups (called "inyenzi", or "cockroaches", by the Hutu government), who launched attacks into Rwanda. The largest occurred in late 1963, when a surprise attack approached Kigali. The government fought back, defeating the rebels and killing thousands of the remaining Tutsi in Rwanda. No further threat was posed by the refugees until the 1990s, when a civil war initiated by the Tutsi-refugee Rwandan Patriotic Front (RPF) forced the Hutu government into negotiations. This led to a rise in Hutu extremism and the 1994 genocide, in which over half a million Tutsi were killed before the RPF took control.