Poles apart in a desert landscape

In the 1980s, the central African nation of Chad was an important and long-running Cold War sideshow. It is a country divided between the Muslim north and the south, where the inhabitants are Christians and followers of traditional religions. On independence in 1960, civil war was imminent. France had bequeathed rule to the southerners and, with Sudanese backing, a Muslim rebel group, Frolinat, was formed in the Darfurian town of Nyala in 1965.

The following decade, Libya's leader, Colonel Muammar Gaddafi, entered the war, laying claim to a strip of territory along the two countries' common border and proclaiming "unity" between Libya and Chad. He backed factions of Frolinat, which he provided with bases, arms and training. In response, the US and French supported other factions. President Reagan, who harboured a personal animus against Gaddafi, upgraded this to the largest CIA operation in Africa and, like the contemporary and larger US support to the Afghan Mujahidin, won a military victory by proxy. The Libyan Army was routed by nimble Jeep-mounted Chadian fighters in the oasis of Ouadi Doum in 1987. Like the Afghan conflict, the Chadian confrontation left a legacy of armaments, factional politics and extremism. In the immediate aftermath, one of the factions Gaddafi backed - the Conseil Democratique Revolutionnaire headed by warlord Acheikh Ibn Oumer - fled to Darfur. They were pursued by a joint French-Chadian expeditionary force and, with his vehicles burned and troops scattered, and his Libyan support cut off, Ibn Oumer threw in the towel. He submitted to President Hiss ne Habre at the end of 1988 - but not before he had distributed weaponry to his Darfurian Arab hosts and unleashed a short but vicious war between Arabs and Fur. This was the origin of the infamous Janjaweed.

Millard Burr and Robert Collins's book, which was originally published in 1999 under the title Africa's Thirty Years' War , documents the twists and turns in this long-running saga. The first edition ended its story in 1991 after Habré had been overthrown by one of his former commanders, Idriss Déby, who mobilised his Zaghawa kinsmen on both sides of the Sudan-Chad border and invaded from Darfur with the backing of Sudan and Libya. Deby, it seemed, at last brought a measure of stability. Gaddafi had pulled in his horns and Deby had made a simple pact with Sudan's President Omer al Bashir: each would secure his side of the border from incursions by the other's rebels. For a decade, the deal held. But Deby's promises faded into a mire of corruption and patrimonialism, despite revenue from Chad's newfound oilfields. His bigger problem was that he could not keep his side of the bargain with Sudan. In 2003, when the Darfurian Zaghawa rebelled, they got support from their brethren in Chad. In the meantime, Bashir's Government turned a blind eye to the discontent in Darfur, then cynically and brutally unleashed the Janjaweed to suppress the rebellion.

This edition brings the story almost up to date, tracing the outbreak of the Darfur war in 2003 and the Sudan Government's vicious response. Since 2005, war has returned to Chad, not least because Bashir contends that the best way to find a military solution is to remove Deby from power and cut off Chadian support to the rebels. What is now Africa's 40-years' war is yet unfinished.

Alex de Waal is a programme director at the Social Science Research Council and author, with Julie Flint, of Darfur: A Short History of a Long War .