The Strategy of Open City Gates
When the enemy is superior in numbers and your situation is such that you expect to be overrun at any moment, then drop all pretence of military preparedness and act casually. Unless the enemy has an accurate description of your situation this unusual behavior will arouse suspicions. With luck he will be dissuaded from attacking.
Three Kingdoms Period China
In 149 BC, the famous strategist Kong Ming of Shu, launched an attack against the state of Wei by sending an advance force to scout for the enemy. Leading the army of Wei was Suma-I who also sent an advance force of fifty thousand troops. The two vanguards met and engaged in battle but the Wei forces were superior and won the day. The defeated Shu vanguard raced back to the main body of Kong Ming's army whose troops, seeing the look of fear in the faces of their comrades, thought that the enemy was upon them and fled in panic. Kong Ming and a few bodyguards fled to the city of Yangping with the Wei army in hot pursuit. Vastly outnumbered and unable to either retreat or sustain a siege, Kong Ming played a last resort strategy that made him famous throughout China. He removed all the guards and battle flags from the walls and had all four of the city gates flung open. When Suma-I approached the city he could see only a few old men nonchalantly sweeping the grounds within the gates. Kong-Ming was seen sitting in one of the towers smiling and playing his lute. Suma-I remarked to his advisors: "That man seems to be too happy for my comfort. Doubtless he has some deep laid scheme in mind to bring us all to disaster." As they stood spell bound, the strains of Kong Ming's lute reached their ears and this only heightened their sense of foreboding. Such peculiar behavior was too suspicious and, fearing a clever trap, Suma-I turned his army back and retreated. After the army left Kong Ming and his remaining troops departed in the opposite direction and made their way safely back to their capital.