兵守

A state that faces enemies on four sides values defensive warfare; a state with its back to the sea values offensive warfare. A state surrounded on four sides that loves to raise armies to resist all four neighbors will be in peril. When each of the four neighboring states raises forces once, the surrounded state must raise its forces four times — therefore it is said the state is in peril. A state surrounded on four sides that cannot use a city of ten thousand households to quarter an army of enormous size will be in peril. Therefore it is said: a state surrounded on four sides must focus on defensive warfare.

In defending a walled city, it is better to use the strength of the 'dead' against the 'living' strength of the attackers. When sections of the wall are breached, that is the strength of the 'dead' — if the attackers do not completely level the wall, they have no way to enter. This is called using the strength of the dead against the living strength of the attackers. When the wall is completely leveled and the attackers have a way to enter, the attackers will inevitably be exhausted while the defenders inside will be rested. Fighting with rested strength against exhausted strength — this is called using the living strength of the people against the dead strength of the attackers. Everyone says: 'The worry of a besieged city is that all will die along with the city.' These three situations are not caused by insufficient resources but by the general's errors.

The way of defending a city lies in maximizing strength. Therefore when facing the enemy, manage the rosters and dispatches and divide the army according to the number of the enemy's scouting chariots.

The three armies: able-bodied men form one army; able-bodied women form one army; the elderly and weak of both sexes form one army — these are called the three armies. The army of able-bodied men is to eat their fill, sharpen their weapons, form ranks, and await the enemy. The army of able-bodied women is to eat their fill, carry the ramparts, form ranks, and await orders. When the attackers arrive, they construct earthworks as obstacles and dig traps and pitfalls; they demolish bridges and tear down buildings, supplying materials as needed — what will not take water they dry out with fire — so the attackers cannot use anything to assist their siege equipment. The army of the elderly and weak is to tend the cattle, horses, sheep, and pigs, and to collect all edible plants and grasses and prepare food from them, in order to supply the food for the able-bodied men and women. But take great care that the three armies do not intermingle. If the able-bodied men pass through the army of able-bodied women, the men will become attached to the women, treacherous people will find opportunity to conspire, and the state will be lost — they will give things away, fear that news will leak, and the brave will not fight. If the able-bodied men and women pass through the army of the elderly and weak, the old will make the young grieve and the weak will make the strong feel pity. With grief and pity in their hearts, the brave will have second thoughts and the timid will not fight. Therefore it is said: take great care that the three armies do not intermingle. This is the way of maximizing strength.