To correct Uokko on two points. One, you can use spies on your own provinces by using them on an enemy province but not confirming the action until you exit from their province and select your own one.
Secondly, Bribe Defenders gives you +13% (or was it 25%) to the siege process instantly on success of the spy, to a maximum of 100%. Great for those level 5&6 forts, Marches and when you want some rebels to take enemy land asap. Cannons give an increased chance of bringing down a fort, bride defenders gives a flat % in siege progress.
Troop desertion can be great for murdering enemy troops when they are all focussed in one area, particularly a non-core province of their's.
Secondly, Bribe Defenders gives you +13% (or was it 25%) to the siege process instantly on success of the spy, to a maximum of 100%. Great for those level 5&6 forts, Marches and when you want some rebels to take enemy land asap. Cannons give an increased chance of bringing down a fort, bride defenders gives a flat % in siege progress.
Troop desertion can be great for murdering enemy troops when they are all focussed in one area, particularly a non-core province of their's.