Reproduction requires 3 players. Players A and B are allies, and are both at war with player C.

1. A should besiege a city belonging to C.

2. C should surrender to B, and give up the city under siege from A.

3. From A's point of view, the city is still besieged. In A's UI, the city is owned by B but they are still "in a battle" against C. If A attempts to assault the city, the game softlocks since the battle will not progress beyond deployment.