Rwandan genocide training to the Banyamulenge, a Tutsi group in the Zairian South Kivu province, helping them to defeat Zairian security forces. Rwandan forces, the Banyamulenge, and other Zairian Tutsi, then attacked the refugee camps, targeting the Hutu militia. These attacks caused hundreds of thousands of refugees to flee; many returned to Rwanda despite the presence of the RPF, while others ventured further west into Zaire. The defeated forces of the former regime continued a cross-border insurgency campaign, supported initially by the predominantly Hutu population of Rwanda's northwestern provinces. By 1999, a programme of propaganda and Hutu integration into the national army,
Hutu of Rwandan national unity, but has been criticized as an attempt at historical revisionism. Still others suggest that the two groups are related but not identical, and that differences between them were exacerbated by Europeans, or by a gradual, natural split, as those who owned cattle became known as Tutsi and those who did not became Hutu. Mahmood Mamdani states that the Belgian colonial power designated people as Tutsi or Hutu on the basis of cattle ownership, physical measurements and church records. There is an ongoing debate as to whether the Hutu and Tutsi are really separate groups or not;