Efforts by the Organization of African Unity (OAU) through most of 1979 brought temporary reconciliation among the warring factions. Nigeria acted as host to four conferences--the first two in Kano and the second two in Lagos--that gave rise to the Transitional Government of National Unity (Gouvernement d'Union Nationale de Transition--GUNT). Goukouni served as president, Wadel Abdelkader Kamougué of FAT as vice president, and Habré as minister of defense in the government. An African peacekeeping force composed of units from Benin, Congo, and Guinea was also scheduled to be sent to Chad. The units from Benin and Guinea failed to arrive, however, and the 600 Congolese who appeared in January 1980 were withdrawn three months later without becoming involved in any military action.
The formation of GUNT did not end conflict among the factional armies. Both Goukouni's FAP and Habré's FAN occupied parts of N'Djamena during the negotiations of 1979 and after the coalition government was installed, maintaining separate spheres of influence radiating from their respective headquarters. When skirmishes broke out in the capital in March 1980, fighting between FAP and FAN gradually escalated. In spite of brief cease-fires and efforts at mediation, the struggle persisted for nearly nine months without much change in the positions of the combatants. Artillery exchanges reduced much of the capital to rubble. Civilian casualties were high, even though most of the remaining population had taken refuge in nearby towns in Cameroon and Nigeria. Under Kamougué FAT cooperated with Goukouni's GUNT coalition, but its attacks from the east on FAN failed. Despite FAT's attacks, FAN managed to preserve its supply lines from Sudan by maintaining control over the N'Djamena-Abéché road.
Although French troops were still present, they did not intervene. They deferred willingly to the efforts of the African nations to restore peace and at Goukouni's request departed in May 1980. FAN's superior firepower and discipline, however, was gradually imperiling the GUNT coalition and led Goukouni to turn to Libya for help. GUNT and Libya signed a treaty of friendship and cooperation on June 15, 1980. Under the treaty, the Chadian government had the right to call upon Libya should Chad's independence, territorial integrity, or internal security be threatened. Armed with this legal pretext, Libya sharply increased its involvement in the country. After Habré resumed his offensive against GUNT in October 1980, Goukouni shifted the FAP's operations to Borkou-Ennedi-Tibesti Prefecture, where, stiffened by Libya's backing, his force ousted FAN from the main settlements. In the meantime, a substantial Libyan force of 7,000 to 9,000 troops accompanied by tanks and self-propelled artillery was transported southward from assembly points in southern Libya. With military advisers from the German Democratic Republic (East Germany) and the Soviet Union coordinating its movements, FAP seized the town of Ati on the N'Djamena-Abéché road, cutting Habré's supply line to the east. The Libyan army, which included 4,500 to 5,000 members of the Islamic Legion, was then moved into position for a strike at N'Djamena. After a week of intensive shelling, FAN was forced to evacuate the capital on December 15, 1980.
With the Libyans present in force, a period of relative calm ensued, although the various regions of the country remained divided under the control of rival military factions. The Libyan army occupied N'Djamena and was posted at bases in northern Chad alongside Goukouni's FAP; the latter's strength was estimated at over 5,000. Kamougué's FAT, comprising some 3,000 to 5,000 troops, occupied the south. The pro-Libyan Democratic Revolutionary Council (Conseil Démocratique Révolutionnaire--CDR), led by Acyl Ahmat, had about 3,000 men in Arab areas of the east. Habré's defeated FAN, numbering no more than 4,000 troops, had retreated to its original stronghold in Biltine Prefecture and along the Sudanese border.
On January 6, 1981, Goukouni signed an accord with Qadhaafi to merge Chad and Libya, evoking a highly negative reaction among the Chadian factions and other African states. Under sustained pressure from African nations and from France to sever his dependence on Libya, Goukouni in effect later renounced the plan of unification and called for the withdrawal of the Libyan forces. Although Qadhaafi's army had become highly unpopular and hundreds of his soldiers had become casualties of guerrilla activity, the haste with which he pulled back the Libyan units within a two-week period in November 1981 came as a surprise.
The Libyans were replaced by an OAU peacekeeping force, the Inter-African Force (IAF), consisting of 2,000 Nigerians, 2,000 Zairians, and 800 Senegalese. Originally, seven African governments had promised contributions, but disputes over financing limited the OAU operation. Because of the vague mandate of the peacekeeping force and the determination of all three countries to avoid combat, the IAF made no effort to block Habré's military comeback after the departure of the Libyans.
Data as of December 1988