In the spring of 684 BC, the powerful State of Qi sent troops to attack the weak State of Lu. Duke Zhuang of Lu personally led the army to war, and the two sides lined up to prepare for a big battle. A general of Lu led his army to fight against Qi. The fighting at that time was beating gongs and drums as an attack call. When the Qi army beat the drums for the first time, Cao Gui held his ground. When the Qi army beat the drums for the second time, Cao Gui still didn't give an order. When the Qi army was preparing for the third attack, they didn't see the Lu army. Morale is greatly reduced and I am very tired. They were suddenly depressed and thought that Lu Jun would not fight again. Everyone sat down to rest and the team began to relax. At this moment, Cao Gui made a decisive decision and said to Duke Zhuang of Lu: It's time to attack. "With the rain of drums, the soldiers of the Lu army who have been rubbing their hands for a long time fought bravely. Before Qi could guard against it, he suddenly panicked and fled everywhere. After the battle was won, Duke Zhuang of Lu asked Cao Gui, "Why did the Qi army beat drums three times before leaving the army? Cao Gui said: "The most important thing in a battle is courage. When playing drums for the first time, the morale is the highest; When the drum was played for the second time, the soldier's courage had weakened; When he hit the drum for the third time, the soldier's courage disappeared. At this time, our army will beat the drums again, and hit the slack and tired army with high morale. Sure, we can win! "