[MaxWilson]

You've been unlucky. I have used this trick too, and it works just as well against the AI as it does against you. However, in order to "catch" the enemy army, you have to:

1.) Originate in the same province that the enemy is moving to, and be headed toward the same province he's coming from.
2.) Either have a largish army or get lucky. The chance of interception is somehow based on the size of the armies, and if both armies are small they can "pass through" each other.

-Max

P.S. BTW, if you really do have an unstoppable army of hundreds, this is a good reason to split them into two or more columns. It's a lot harder for the opponent to stop both columns, even if he knows exactly what province you'll be moving into--then the delayed column just catches up. On the other hand, if your army is NOT unstoppable this invites defeat in detail.

P.P.S. One other possibility--it *might* depend upon which nation you're playing. I know that if two EA nations both attempt to move into an indy province on the same turn, and one of them is Abysia, Abysia will always attack the indies first and will therefore be the defender in the battle.