Hefei covered the southern approach to the central plains. Cao Cao’s colonies and garrison made it the first hard wall Wu met going north. In 215 Zhang Liao struck Sun Quan’s army at Xiaoyao Ford outside the city.
Wei later built a new fortress northwest of the old city. Sun Quan and Zhuge Ke still could not take it. Wu’s northern edge stayed between Chao Lake and the Huai, not at Xu or Luoyang.