In February 246, when Eastern Wu forces attacked Zhazhong, over 10,000 households living in the area fled to the north across the Mian River (, a historical name for the Han River). When news of the Wu invasion reached the Wei imperial court, Sima Yi argued that they should let the civilians remain on the north side of the Mian River since the south side was near enemy territory and hence too dangerous for them. However, Cao Shuang said: "It isn't in our long-term interests to allow the civilians to remain here and give up trying to secure the south of the Mian River." Sima Yi disagreed: "If the enemy sends 20,000 troops to cut off passage across the Mian River, sends another 30,000 troops to fight our forces at the south of the Mian River, and sends another 10,000 troops to occupy Zhazhong, what can we do to save those civilians?" Cao Shuang refused and ordered the refugees to return to the south of the Mian River. As Sima Yi foresaw, the Wu forces occupied Zhazhong, captured the civilians, and relocated them to Wu territory.