The "catching a turtle in a jar" strategy is a political stratagem. After the Battle of Red Cliffs, Cao Cao had been looking for an opportunity to eliminate Sun and Liu, but he was afraid that Ma Teng would attack Xuchang. So, Xun You suggested that Cao Cao use the authority of Emperor Xian of Han to promote Ma Teng as the General Who Conquers the South, ordering him to fight against Sun Quan, luring him into the capital, and then eliminating him. This strategy within a strategy is a sub-strategy within the greater strategy of attacking distant enemies while making peace with closer ones.