When a friend does not come to terms, intrigue should be frequently resorted to. Through the agency of spies, the friend should be won over after separating him from the enemy. Or attempts may be made to win him over who is the last among combined friends; for when he who is the last among combined friends is secured, those who occupy the middle rank will be separated from each other; or attempts may be made to win over a friend who occupies middle rank; for when a friend occupying middle rank among combined kings is secured, friends, occupying the extreme ranks cannot keep the union. (In brief) all those measures which tend to break their combination should be employed.