In 318 AD, Sima Rui, the Prince of Langya, established the Eastern Jin Dynasty with the support of the Wang brothers, Wang Dao and Wang Dun. Emperor Yuan of Jin appointed Wang Dao as his prime minister and Wang Dun as Grand General and Governor of Jingzhou, stationed in Wuchang.
In 322 AD, the warlord Wang Dun sensed that Emperor Yuan of Jin was consolidating power and gradually distancing himself, weakening Wang Dun's influence. Determined to strike first, Wang Dun began plotting a rebellion.
Before launching his campaign from Wuchang, the warlord Wang Dun sent word to the general Gan Zhuo, governor of Liangzhou, urging him to join the eastward march. Gan Zhuo initially agreed, but as the departure neared, he had a change of heart and dispatched his aide Sun Shuang to Wuchang to dissuade Wang Dun from rebellion. Wang Dun defended himself, saying, "General Gan misunderstands me. I am merely removing the emperor's corrupt advisors, not opposing the throne. If we succeed, I will reward him with a noble title."
When Sun Shuang reported back to Gan Zhuo, Gan Zhuo was torn and couldn't make up his mind. Just then, Sima Cheng, the governor of Xiangzhou who had openly opposed Wang Dun's rebellion, sent his secretary Deng Qian to Xiangyang. Deng Qian urged Gan Zhuo, "Stay loyal to the court and raise an army to crush Wang Dun."
Still uncertain, Gan Zhuo gathered his subordinates to discuss the matter. Staff officer Li Liang advised him, "I believe you should hold your troops steady and not act hastily. If Wang Dun wins, he will surely honor you; if Wang Dun loses, the imperial court will command you to raise an army to suppress the rebellion. Either way, victory will work to your advantage."
Deng Qian countered, "General, you must not heed Advisor Li's counsel. If you sit on the fence, disaster will follow. Remain idle, and Wang Dun will hold a grudge; the court will also distrust you. In truth, Wang Dun commands no more than ten thousand troops, with only five thousand guarding Wuchang. Your forces are double his. If you raise an army against him and strike directly at Wuchang, it will be like crushing dry weeds and smashing rotten wood—victory is certain!"
But Gan Zhuo remained hesitant. As Wang Dun marched eastward without seeing Gan Zhuo's support, he sent his advisor Le Daorong to Xiangyang to urge Gan Zhuo to join. Unexpectedly, Le Daorong opposed Wang Dun's rebellion and instead advised Gan Zhuo, "You should raise an army to punish Wang Dun." Gan Zhuo, persuaded by Le Daorong's words, then allied with the Prefect of Nanping and others to launch a campaign against Wang Dun.
When Wang Dun learned that Gan Zhuo had raised an army to attack him, he knew he was no match and sent Gan Zhuo's nephew, the military advisor Gan Ang, to plead with his uncle, saying, 'Please understand my difficult position, return to Xiangyang, and let us make peace.' Gan Zhuo, indecisive by nature, actually believed Wang Dun's words and withdrew his forces.
Wang Dun finally succeeded in his rebellion. Later, he conspired with Zhou Lü, the governor of Xiangyang, and secretly assassinated Gan Zhuo.
Later, the idiom "crushing dry weeds and smashing rotten wood" came to describe something or an enemy that is very easy to destroy.
Source: *Book of Jin*, "Biography of Gan Zhuo"
Meaning of the Idiom: Later, the Chinese idiom "摧枯拉朽" came to describe how something or an enemy that is very easy to destroy.