3. Attack by Stratagem
Thus the highest form of generalship is to balk the enemy's plans;
Perhaps the word "balk" falls short of expressing the full force of the Chinese word, which implies not an attitude of defense, whereby one might be content to foil the enemy's stratagems one after another, but an active policy of counter-attack. Ho Shih puts this very clearly in his note: "When the enemy has made a plan of attack against us, we must anticipate him by delivering our own attack first."
Isolating him from his allies. We must not forget that Sun Tzu, in speaking of hostilities, always has in mind the numerous states or principalities into which the China of his day was split up.
When he is already at full strength.
and the worst policy of all is to besiege walled cities.