karnak1: Can anyone please explain to me how the "assassination" option can be useful? I've never really understood how it can help your game.
Because even if you manage to assassinate a fierce rival there's a good probability that his heir will become even more embittered towards you.
You can assassinate a competitor for inheritance. Say you’re older brother is set to inherit a title you want, send an assassin and suddenly you’re next in line (Castille and Leon have a dynamic like this in play in 1066, assassinate your brother before he has a male child and you get both kingdom titles). You can also assassinate powerful enemy court members to reduce the ratings of the king of a rival kingdom you plan to invade. If you really spend a lot of time and money you might even be able to kill off all his male court members and his armies will then have no generals in command, this can be a huge advantage if your forces are relatively even.
There are lots of reasons why you might need the option, just put a little thought into a problem you face and ask yourself if an assassin might help you resolve said problem. It’s not an uber overpowered option like in some games, buts it’s a nice tool to have on your tool belt.
Jim