Ask Lemmygrad

The Angolan Civil War is a very strange period of history for me. By all logic it doesn't make sense that there are not only two large, powerful communist parties but that they were fighting each other - with one even being backed by the West of all people. I've heard the division was caused primarily by an ethnic dispute with the two parties representing two different ethnicities.

Is this accurate or was there more to it than that? I'd appreciate any insight anyone has - or at least resources if available - in order to better understand why this war happened.