AI in Might & Magic: Heroes VI

I agree. That's exactly how I managed to trap him (because catching up is impossible). The main hero leaves the castle without troops to meet the enemy (but not too close). The castle is also empty. And when the enemy approaches, the hero with an army (not the main one) teleports to that castle, gives everything to the main hero (who is slightly ahead), and he defeats the enemy.

In general, speaking in chess terms, the AI looks one step ahead, and any combinations of 2 or more actions are "invisible" to it. Literally, a two-move combination puts it in a dead end.