Beginning in the 7th millennium BC, human populations moved into the Chadian basin in great numbers. By the end of the 1st millennium AD, a series of states and empires had risen and fallen in Chad's Sahelian strip, each focused on controlling the trans-Saharan trade routes that passed through the region. France conquered the territory by 1920 and incorporated it as part of French Equatorial Africa. In 1960, Chad obtained independence under the leadership of François Tombalbaye. Resentment towards his policies in the Muslim north culminated in the eruption of a long-lasting civil war in 1965. In 1979 the rebels conquered the capital and put an end to the South's hegemony. But, the rebel commanders fought amongst themselves until Hissène Habré defeated his rivals. The Chadian–Libyan conflict erupted in 1978 by the Libyan invasion which stopped in 1987 with a French military intervention (Operation Épervier). Hissène Habré was overthrown in turn in 1990 by his general Idriss Déby. With French support, a modernization of the Chad National Army was initiated in 1991. Since 2003 the Darfur crisis in Sudan has spilt over the border and destabilised the nation. Poor already, the nation and people struggled to accommodate the hundreds of thousands of Sudanese refugees who live in and around camps in eastern Chad.