Within the complex and changing foreign relations triangle comprising Chad, France, and Libya, the large nations of Nigeria and Sudan were also important actors. Nigeria considered France its primary rival in its attempt to chart the course of West Africa's political development. Its generally paternalistic relations with Chad intensified after the coup that ousted President Tombalbaye in 1975. After that, limiting Libyan expansion while avoiding direct clashes with Libyan troops also became important goals. Nigeria sponsored talks among Chad's rival factions in 1979 and promoted a little-known civil servant, Mahmat Shawa Lol, as a compromise head of a coalition government. Lol's perceived status as a Nigerian puppet contributed to mounting opposition during his short term as president in 1979.

The two nations forged stronger ties during the 1980s. Hoping to benefit commercially and diplomatically by expanding regional trade relations, Nigeria replaced France as Chad's major source of export revenues. Bilateral trade agreements involved Chadian exports of livestock, dried fish, and chemicals and imports of Nigerian foodstuffs and manufactured goods. Both governments also recognized the potential value of the large informal trade sector across their borders, which neither country regulated. In addition, Nigerian industry and commerce employed several thousand Chadians workers.

Chad's relationship with Nigeria was not without its strains, however. Beginning in the late 1970s, clashes occurred around Lake Chad, where both countries hoped to exploit oil reserves. Both also sought to defuse these confrontations, first by establishing joint patrols and a commission to demarcate the boundary across the lake more clearly. Then in the early 1980s, the low level of Lake Chad brought a series of tiny islands into view, leading to further disputes and disrupting long-standing informal trade networks.

This relationship was also complicated by Nigeria's own instability in the north, generated by rising Islamic fundamentalism. Thousands of casualties occurred as the result of violent clashes in Nigeria throughout 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.

Sudan, Chad's neighbor to the east, responded to Chad's conflict with Libya based on its own regional, ethnic, and cultural tensions. In Sudan, the Islamic northern region had generally dominated the non-Muslim south. Sudan's ties with Libya, although cautious during the 1970s, warmed during the 1980s, strengthb0d thening N'Djamena's fears of insurgency from the east.

The populations of eastern Chad and western Sudan established social and religious ties long before either nation's independence, and these remained strong despite disputes between governments. Herdsmen in both countries freely crossed the 950-kilometer border, seeking pastureland and water sources as they had for centuries. Muslims in eastern Chad often traveled through Sudan on the hajj, or annual pilgrimage to Mecca, and many young people from eastern Chad studied at Islamic schools in Sudan. In addition, Sudan's cotton plantations employed an estimated 500,000 Chadian workers in 1978.

At the same time, the basis for political enmity between these two nations was set in the early 1960s, when Chad's southern bias in government offended many Sudanese Muslims. Sudan allowed FROLINAT rebels to organize, train, and establish bases in western Sudan and to conduct raids into Chad from Sudan's Darfur Province. Refugees from both countries fled across their mutual border.

Following the coup that ousted Tombalbaye in 1975, relations between presidents Jaafar an Numayri and Malloum were surprisingly cordial, in part because both nations feared Libyan destabilization. Sudan sponsored talks among Chad's rebel army leaders in the late 1970s and urged Malloum to incorporate them into his government. (Numayri promoted the talents and intelligence of Habré, in particular, and persuaded Malloum to appoint Habré to political office in 1978.) These ties were strained in part because of Numayri's warming relations with Libyan leader Qadhaafi.

As violence in Chad increased between 1979 and 1982, Sudan faced its own internal rebellion, and relations deteriorated after Numayri was ousted in 1983. In 1988 Habré assailed Sudan for allowing Libyan troops to be stationed along Chad's border and for continuing to allow assaults on Chadian territory from Sudan.

Data as of December 1988