I often see undamaged units that don't seem to be under threat make a self-retreat back to HQ. Have I have missed some element of game play that causes units to retreat on their own, or is this a bug? It's very annoying, and has caused me grief in tightly-contested battles, when a vital unit just takes off and dashes back to HQ.
I didn't make it!
Maybe the Axis player uses forced retreat: that means your units in a certain area retreat.