How to win German Campaign Mission 2?

[Felis]

So I'm playing this mission, and in the middle of it, I decide that I'm fed up with defending on crowded terrain, and make a full scale assault on the Allied position, taking both of their giant howitzers.

However, the game continues to spawn Crusader tanks and infantry every so often, and I've hijacked three of them.

Am I missing something? The game just isn't ending. I've destroyed every enemy on the screen. The objective tells me to "Stop the enemy from breaking through on the right flank".

There ARE no enemies, just the two Crusader tanks that keep respawning and keep getting vaporized by the approximately 50 gigantic guns I have watching the border. There is literally a PILE of tanks.

Am I failing to complete some obscure requirement?