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.
With regard to precipitous heights, if you are beforehand with your adversary, you should occupy the raised and sunny spots, and there wait for him to come up.
Hence the saying: If you know the enemy and you know yourself, your victory will not stand in doubt; if you now Heaven and you know Earth, you may make your victory complete.
Humble words and increased preparations are signs that the enemy is about to advance. Violent language and driving forward as if to the attack are signs that he will retreat.
If an enemy has alliances, the problem is grave and the enemy's position strong; if he has no alliances, the problem is minor and the enemy's position weak.