The roots of the war reached back to the cartographers of colonial France. When the Republic of Upper Volta and the Republic of Mali both gained independence in 1960, they inherited a frontier in the northeast that had never been properly demarcated. The Agacher Strip, a band of scrub around the Béli River, was claimed by both. Upper Volta pointed to old 1920s maps showing the border villages within its colony. Mali pointed to its herders, who had long established communities there to reach the grazing land. There were rumors of valuable manganese deposits beneath the soil, though little evidence they truly existed. After armed clashes flared in 1974, the two countries finally agreed to let the International Court of Justice settle the matter.

By 1985 the legal process had stalled and tempers had frayed. Burkina Faso's revolutionary president, Thomas Sankara, had publicly called for a revolution in neighboring Mali, while Mali's president Moussa Traoré governed a country in economic distress. When Burkinabé census workers entered the disputed villages that December, the spark caught. At dawn on 25 December, Malian forces struck with aircraft and tanks. Outgunned, Burkinabé troops fell back into guerrilla tactics, trying to stall the armored columns. Civilians were caught directly in it, bombed from the air and overrun on the ground. Mali soon held most of the strip. A ceasefire came on 30 December, mediated by neighboring West African states, ending the killing as abruptly as it had begun.

A year later, on 22 December 1986, the International Court of Justice delivered the verdict the two governments had once asked it to make. The court split the Agacher Strip in two, granting Mali the more populated western portion and Burkina Faso the eastern section around the Béli, and both nations accepted the ruling. Diplomatic relations had already been restored that June, and Sankara and Traoré had shaken hands at a regional summit. The war left its marks on both sides: it dented the credibility of Burkina Faso's revolutionary leaders, who afterward struck a more moderate tone abroad, while in Mali it briefly lifted the standing of Traoré's struggling government. The Agacher Strip War remains the only full interstate war ever fought over territory in West Africa since the end of colonial rule - a small, sharp tragedy over an empty patch of desert, remembered for the families it scarred at Christmas.