Quote Originally Posted by YourLordandConqueror
The main Reason I was asking was that I had a theory based on a earlier thread, in that AI factions do not regard using assassin's and spies as aggressive actions because of the inherent use of the princess, which essential works as a higher valour emissary.
Martok is right, there must be a state of peace in order to inherit lands. I don't think an alliance is necessary but if you are at war no.

Subterfuge does not count as aggressive acts. And you cannot discover which faction killed your agents/generals. If you catch rival assassins in your provinces you will occasionally be informed of the identity of his employers, or the suspected identity as the parchment calls it ("he was believed to be working for the..." etc). These are assassins (or spies) that are caught by the border forts or counterspying agents. Such assassins/spies may not have been targeting your agents/generals but may have been simply passing through. If one of your agents/generals does fall to an assassin you won't know who he was working for as he will have escaped. You can guess, but it is not revealed in black and white, nor are there any repercussions or an "international incident" of any kind. The same goes for the AI. It too will not know which faction is sending spies after it's agents/generals, so you can assassinate at will without any worries of it harming diplomatic relations, starting a war, breaking an alliance or anything else. Subterfuge in MTW is on an almost entirely invisible level.