You have attempted this on previous occasions. It is no long-term solution and the Douglas family are more powerful than you think. They have a dense network of connections throughout Scotland.
Arrange a meeting with the 8th Earl of Douglas. You want to see an end to all this feuding.
Which card will you play?
Arrange a meeting with the Lords of the Isles and bribe them into double-crossing the 'Black' Douglases. This will strengthen the Crown's relations in the west and get rid of the Douglas threat to your ambitions.