Hall of Doh!

[lch]

MaxWilson said:
I'm pretty sure the troops would have died anyway even if you had had a second commander stealthed in the same province.

Dunno if you're the actual enemy in whose lands he was hiding, but I think he referred to the fact that an army without any commanders among them flee instantly if involved in a battle without fighting. And if they do it while being surrounded in enemy territory, then they all die during the retreat attempt.