In the times of Zhuge Liang's northern offensives, the state of Wu had always been on the defensive against invasions from the north. The area around Hefei was the scene of many bitter battles and under constant pressure from Wei after the Battle of Red Cliffs. Warfare had grown so intense that many of the residents chose to migrate and resettle south of the Yangtze River. After Zhuge Liang's death, attacks on the southern Huai River region intensified but nonetheless, Wei could not break through the line of the river defenses erected by Wu, which included the Ruxu fortress.