Still reading that book about Chad on the side.
For me it seems the conflicts in Africa just partially tribal, or motivated by religion. It's liek the Urpian colonists created these artificial entities, the countries, states in Africa, as the avatars of power, and the strongmen of the African countries battling against each other to gain that power (and then to be cast down by another rival).
In Chad only in the beginning the civil war had some tribal coloring, showing the division between north and south, but after Tombolbaye, it's northern strongmen who competes against each other with their personal - partially ex-guerilla, partially mercenary, partially state - armies, with the help of external powers, like was Libya and the always present France.