Cao Cao led his troops to crusade against Zhang Xiu. The weather was surprisingly hot and the sun was like fire. In order to boost morale, Cao Cao said, "There was a great Meilin, forgive the son, and be sweet and sour to quench your thirst." When the foot soldiers smell it, their mouths are full of water, so they can get to the front source.

The matter of "looking for plums to quench thirst" shows Cao Cao's intelligence. He can mention sweet and sour plums when the army is cut off from water and the soldiers are thirsty, which not only causes the soldiers to have a conditioned reflex and temporarily relieve their thirst, but also boosts their morale and "gains the former source". Later, I used the metaphor of "looking at plum to quench my thirst" to make a false claim.