Three noted episodes in the Three Kingdoms

Empty Fort Strategy

During the first Northern Expedition, Zhuge Liang's efforts to capture Chang'an were undermined by the loss at the Battle of Jieting. With the loss of Jieting, Zhuge Liang's current location, Xicheng (西城), was in great danger. With the army deployed elsewhere and left with only a handful of civilian officers in the city, Zhuge Liang decided to use a ploy to ward off the approaching Wei army.

Zhuge Liang ordered all the city gates to be opened and had two soldiers sweeping the roads while he sat high up on the gates calmly playing his zither with two children beside him. When the Cao Wei commander Sima Yi approached the fort with the Wei military, he was uncertain by the scene, and, assuming there was an ambush waiting for his army, retreated his troops.

Zhuge Liang later told the bewildered civil officers that the strategy only worked because Sima Yi was suspicious by nature. Sima had personally witnessed the success of Zhuge Liang's highly effective ambushing and misdirection tactics many times before so he probably felt suspicious when he saw the open scene before him just now. Besides, Zhuge Liang had a reputation as a keen but extremely careful military tactician who rarely took risks. Zhuge Liang's meticulousness, coupled with Sima Yi's suspicions, led Sima Yi to the conclusion that the seemingly empty fort had a hidden ambush inside. It is unlikely the same strategy would have worked on someone else. Indeed, Sima Yi's son Sima Zhao saw through the ruse immediately and advised his father against retreat.

According to Professor Yi Zhongtian, this event could not have taken place due to these reasons; Firstly, Sima Yi was not present at the site where this event took place as he was stationed far away in Wancheng (宛城) according to historical records. Secondly, it was impossible to have gotten to such close proximity to Zhuge Liang to watch his facial expressions and hear him play the zither clearly and if so, the Wei army could have ordered an archer to shoot down Zhuge Liang. Thirdly, based on Sima Yi’s expertise in military strategy, Sima Yi would possibly have ordered his army to surround the city and not attack even if he believed that there was an ambush inside, to verify that his assumption was true.