Quote Originally Posted by Geezer57
I almost always play on Expert level of difficulty, and I've often had the A.I. reinforcements enter at different points when their original entry area was blocked. I get the impression that, when one wave is stymied at some point by your army, a later wave of reinforcements will often appear elsewhere.

If you only play on lower difficulties, you can expect a more predictable A.I.
I've played on 'Normal' and on 'Hard' and the AI seems to always use the same entry-point. I have never played on 'Expert' and probably never will either, based on the way my 'Hard' campaigns have turned out.