In Europa Universalis II, "stealing a siege" happens when a country moves a leader to an ongoing siege, and thereby takes control of it. A human player can often ruthlessly exploit AI allies to siege for him, if he has a leader. Get an AI with a decent army into alliance. Ideally it will not be a major power, since they tend to have leaders of their own. (You can mouse over a potential ally's armies to see if there are any leaders currently; you can also look at their leader file.) Now you declare war on a third party, and invite your ally to the war. The ally will send his armies to siege an enemy province or two; you should concentrate on covering and sieging the enemy's other provinces, avoiding all battles except for sure wins. Eventually the enemy will blunder into your ally. Once you