This story is adapted from the novel Romance of the Three Kingdoms.
During his second northern expedition against the Wei State, Zhuge Liang of Shu led 300,000 troops towards Chencang, a vital communication stronghold of Wei. The defending general, Hao Zhao, had prepared deep trenches and a strong fortress, refusing to engage despite daily challenges from Shu forces.
When a scout reported that Hao Zhao was gravely ill, Zhuge Liang saw his opportunity. He ordered generals Wei Yan and Jiang Wei to take 5,000 troops and surround Chencang within three days, attacking upon seeing a fire signal. Separately, he gave secret orders to Guan Xing and Zhang Bao.
As Hao Zhao's health deteriorated, he was suddenly informed that Shu troops were at the city gates. He urgently ordered a defense, but fires broke out on the watchtowers, causing chaos within the city. Hao Zhao died of fright, and Shu troops overwhelmed the defenders.
Three days later, when Wei Yan and Jiang Wei arrived, they heard a shout from the wall: "You have come too late!" Fixing their gaze upward, they saw Zhuge Liang himself. They hastily dismounted and saluted.
Zhuge Liang explained, "I gave you three days to maintain secrecy. That same night, I sent Guan Xing and Zhang Bao ahead. Disguised among the soldiers, I marched by starlight to launch a surprise attack. The fires were my doing, throwing the city into confusion. This is called 'taking the enemy by surprise and striking when unprepared.'"