In the 7th millennium BC, ecological conditions in the northern half of Chadian territory favored human settlement, and the region experienced a strong population increase. Some of the most important African archaeological sites are found in Chad, mainly in the Borkou-Ennedi-Tibesti Region; some date to earlier than 2000 BC.
For more than 2,000 years, the Chadian Basin has been inhabited by agricultural and sedentary people. The region became a crossroads of civilizations. The earliest of these were the legendary Sao, known from artifacts and oral histories. The Sao fell to the Kanem Empire, the first and longest-lasting of the empires that developed in Chad's Sahelian strip by the end of the 1st millennium AD. Two other states in the region, Baguirmi and Wadai Empire emerged in the 16th and 17th centuries. The power of Kanem and its successors was based on control of the trans-Saharan trade routes that passed through the region.These states, at least tacitly Muslim, never extended their control to the southern grasslands except to raid for slaves.In Kanem, about a third of the population were slaves.
French colonial expansion led to the creation of the Territoire Militaire des Pays et Protectorats du Tchad in 1900. By 1920, France had secured full control of the colony and incorporated it as part of French Equatorial Africa. French rule in Chad was characterised by an absence of policies to unify the territory and sluggish modernisation compared to other French colonies.
The French primarily viewed the colony as an unimportant source of untrained labour and raw cotton; France introduced large-scale cotton production in 1929. The colonial administration in Chad was critically understaffed and had to rely on the dregs of the French civil service. Only the Sara of the south was governed effectively; French presence in the Islamic north and east was nominal. The educational system was affected by this neglect.
After World War II, France granted Chad the status of overseas territory and its inhabitants the right to elect representatives to the French National Assembly and a Chadian assembly. The largest political party was the Chadian Progressive Party (PPT), based in the southern half of the colony. Chad was granted independence on 11 August 1960 with the PPT's leader, a Sara people François Tombalbaye, as its first president.
Two years later, Tombalbaye banned opposition parties and established a one-party system. Tombalbaye's autocratic rule and insensitive mismanagement exacerbated interethnic tensions. In 1965 Muslims began a civil war. Tombalbaye was overthrown and killed in 1975, but the insurgency continued. In 1979 the rebel factions conquered the capital, and all central authority in the country collapsed. Armed factions, many from the north's rebellion, contended for power.
The disintegration of Chad caused the collapse of France's position in the country. Libya moved to fill the power vacuum and became involved in Chad's civil war. Libya's adventure ended in disaster in 1987; the French-supported president, Hissène Habré, evoked a united response from Chadians of a kind never seen before and forced the Libyan army off Chadian soil.
Habré consolidated his dictatorship through a power system that relied on corruption and violence with thousands of people estimated to have been killed under his rule. The president favoured his own Daza ethnic group and discriminated against his former allies, the Zaghawa. His general, Idriss Déby, overthrew him in 1990. Attempts to prosecute Habré led to his placement under house arrest in Senegal in 2005; in 2013, Habré was formally charged with war crimes committed during his rule. In May 2016, he was found guilty of human-rights abuses, including rape, sexual slavery, and ordering the killing of 40,000 people, and sentenced to life in prison.
Déby attempted to reconcile the rebel groups and reintroduced multiparty politics. Chadians approved a new constitution by referendum, and in 1996, Déby easily won a competitive presidential election. He won a second term five years later. Oil exploitation began in Chad in 2003, bringing with it hopes that Chad would at last have some chances of peace and prosperity. Instead, internal dissent worsened, and a new civil war broke out. Déby unilaterally modified the constitution to remove the two-term limit on the presidency; this caused an uproar among the civil society and opposition parties.
In 2006 Déby won a third mandate in elections that the opposition boycotted. Ethnic violence in eastern Chad has increased; the United Nations High Commissioner for Refugees has warned that a genocide like that in Darfur may yet occur in Chad. In 2006 and in 2008 rebel forces have attempted to take the capital by force, but have on both occasions failed. An agreement for the restoration of harmony between Chad and Sudan, signed 15 January 2010, marked the end of a five-year war. The fix in relations led to the Chadian rebels from Sudan returning home, the opening of the border between the two countries after seven years of closure, and the deployment of a joint force to secure the border. In May 2013, security forces in Chad foiled a coup against the President Idriss Deby that had been in preparation for several months.
In 2016, former ruler Hissène Habré was sentenced to life in prison in Senegal for crimes against humanity.