Fighting their forces piecemeal and having your main army tied up in sieges allows the enemy to regroup and gather forces for a counter attack. Not to mention you are always attacking so have the disadvantage of unfavourable terain meaning you will take losses.

If they give up the province without a fight, you lose no men, are ready to rock and roll again next turn and force rapid losses on your opponent, making it hard for him to regroup.

It's more of an opportunity to exploit than an outright strategy though. Say you attack Aragon, which has the enemy king. Rather than risk losing the battle they abandon Aragorn and retreat to Castile.

Next turn starts with the King in Castile and you in Aragon. You promptly move your army into Castile chasing the king and move a bunch of troops in from other provinces to keep Aragon from rebelling.

You end the turn and watch as the King moves out of Castile into Leon and garrisons from other provinces flood into Castile to cover his retreat and they stand and fight.

From what I've found, it can be a very useful trick to pull now and then, but you can't rely on itto work effectively more than once.

Coincidentally, I'm now grinding the Castile Leonese into dust, having taken most of Iberia now. I've made peace with the French, who are suffereing repeated rebellions and have been fighting off the Golden Horde on their eastern border. They were eager for peace, but I'm weary of drawing troops away from my borders in case I invite a counter attack.

They are now sufficiently weakened that I don't have to immediately woory about them dominating the world which is lucky, because I need a chance to solidify my gains and rebuild my navy and trade empire.

For now I'm playing a holding game with the French, leaving my 8* General (and a good number of crack troops that I could really use in Iberia) to guard the border provinces. My main standing army is in Iberia, and while still quite sizable, it needs reinforcements to continue to press the advantage against the CL. They have about 4 provinces remaining to them, one of which is sealed off and isolated. the Crusader States are camped in Morocco and I'm weary of them. I can't afford for them to get involved and come after me as well.

It's a tense time....The XL mod has really proven itself to me, the complexity of the added factions and new units, plus unit restrictions on factions and added combat difficulty add new dimensions to the game.

I've just laid hands on a mercenary Naptha Catapult, can I cant wait to try it out and see what it does. Does it lob a Naptha grenade instead of a regular catapult shot? I've just had a rebellion in Navare so I guess I'll find out soon! stupid rebels, that's what you get for deserting your King.