It is imperative to contest all factions for complete victory, so the army is not garrisoned and the profit can be total. This is the law of strategic siege.
When the common soldiers are too strong and their officers too weak, the result is insubordination. When the officers are too strong and the common soldiers too weak, the result is collapse.
In all history, there is no instance of a country having benefited from prolonged warfare. Only one who knows the disastrous effects of a long war can realize the supreme importance of rapidity in bringing it to a close.
In all fighting, the direct method may be used for joining battle, but indirect methods will be needed in order to secure victory. In battle, there are not more than two methods of attack.. the direct and the indirect; yet these two in combination give rise to an endless series of maneuvers.
Engage people with what they expect; it is what they are able to discern and confirms their projections. It settles them into predictable patterns of response, occupying their minds while you wait for the extraordinary moment - that which they cannot anticipate.
When the leader is morally weak and his discipline not strict, when his instructions and guidance are not enlightened, when there are no consistent rules, neighboring rulers will take advantage of this.