During the Three Kingdoms period, after Liu Bei secured the Western Sichuan region, the tripartite balance of power was established. Soon, Cao Cao and Sun Quan allied in an attempt to seize Jingzhou, which was defended by Guan Yu. To relieve the threat to Jingzhou, Zhuge Liang instructed Guan Yu to launch a preemptive attack on Cao Ren, who was stationed in Xiangyang.
Following orders, Guan Yu swiftly captured Xiangyang. Forced to retreat to Fancheng, Cao Ren sent urgent pleas for aid to Cao Cao in Xuchang. In July of that year, Cao Cao dispatched his top general Yu Jin to reinforce Cao Ren. Guan Yu devised a plan to flood the Seven Armies, crushing Cao Cao's forces, capturing Yu Jin alive, and laying siege to Fancheng.
When Cao Cao learned that Yu Jin had been defeated and that Fan City was in imminent danger, he dispatched his general Xu Huang with reinforcements. Xu Huang, aware of his own insufficient forces, stationed his troops at Yangling Slope, a short distance from Fan City. He then shot an arrow carrying a message into the city to contact Cao Ren, urging him to hold firm and await relief.
At that time, a contingent of Shu troops was stationed in Yancheng, not far from Fancheng. Xu Huang deliberately led his men to dig pitfalls outside the city, as if to cut off Yancheng's escape route. The Yancheng commander fell for the ruse and withdrew, allowing Xu Huang to take Yancheng with ease, forming a pincer position with Fancheng.
Soon, the other reinforcement troops dispatched by Cao Cao arrived and were placed under Xu Huang's command. Seeing his forces significantly bolstered, Xu Huang began to deploy for battle.
Xu Huang knew that Guan Yu's main forces were stationed at Weitou and Sizhong. Feigning an attack on Weitou with a diversionary force, Xu Huang instead led his main army in a surprise assault on Sizhong.
By the time Guan Yu realized he had fallen into the trap, Xu Huang's forces had already charged straight in, covering a thousand li in a single day, and defeated the defenders at Sizhong, pressing directly upon Fancheng. Guan Yu's troops were routed, and the siege of Fancheng was thus lifted.
After receiving Xu Huang's victory report, Cao Cao immediately sent a commendation order to the army, stating, "In over thirty years of military command, among all the ancient generals skilled in warfare I have known, none has matched your ability to drive straight into enemy encirclements!"
Later, the idiom "Long Drive Straight In" came to describe an army advancing with unstoppable momentum, penetrating deep into enemy territory.
Source: *Cao Cao*, "Order Commending Xu Huang"
Meaning of the Idiom: Later, the Chinese idiom "长驱直入" came to describe an army advancing with unstoppable momentum, penetrating deep into enemy territory.