History of Chad Africa's major language groupings south of the Sahara Desert (except Khoisan, which is not considered a valid genetic grouping anyway), i. e. the Afro-Asiatic, Nilo-Saharan and Niger–Congo phyla, originated in prehistoric times in a narrow band between Lake Chad and the Nile Valley. The origins of Chad's peoples, however, remain unclear. Several of the proven archaeological sites have been only partially studied, and other sites of great potential have yet to be mapped. At the end of the 1st millennium AD, the formation of states began across central Chad in the sahelian zone between the desert and the savanna. For
Chad–Nigeria relations the 1980s. Most religious violence was domestic in origin, but Nigerian police arrested a few Libyans, and Nigerian apprehension of Libyan infiltration through Chad intensified. Nigeria's 1983 economic austerity campaign also produced strains with neighboring states, including Chad. Nigeria expelled several hundred thousand foreign workers, mostly from its oil industry, which faced drastic cuts as a result of declining world oil prices. At least 30,000 of those expelled were Chadians. Despite these strains, however, Nigerians had assisted in the halting process of achieving stability in Chad, and both nations reaffirmed their intention to maintain close ties. In May 2014, in