The major configurations (hsing) of terrain are accessible, suspended, stalemated, constricted, precipitous, and expansive. If we can go forth and the enemy can also advance, it is termed ‘accessible.’ In an accessible configuration, first occupy the heights and yang [sunny side], and improve the routes for transporting provisions. Then when we engage in battle, it will be advantageous. If we can go forth but it will be difficult to return, it is termed ‘suspended.’ In a suspended configuration, if they are unprepared go forth and conquer them. If the enemy is prepared and we sally forth without being victorious, it will be difficult to turn back and is not advantageous. If it is not advantageous for us to go forth nor advantageous for the enemy to come forward, it is termed “stalemated.' In a stalemated configuration, even though the enemy tries to entice us with profit, we do not go forth. Withdraw our forces and depart. If we strike them when half the enemy has come forth, it will be advantageous. As for constricted configurations, if we occupy them first we must fully deploy throughout them in order to await the enemy. If the enemy occupies them first and fully deploys in them, do not follow them in. If they do not fully deploy in them, then follow them in. As for precipitous configurations, if we occupy them we must hold the heights and yang [sunny side] to await the enemy. If the enemy occupies them first, withdraw our forces and depart. Do not follow them. As for expansive configurations, if our strategic power is equal, it will be difficult to provoke them to combat. Engaging them in combat will not be advantageous.
Sun Tzu, The Art of War, c. 450 BCE