Ma Su's forces encountered Zhang He's forces at Jieting. It was here that Ma Su made a serious tactical blunder. He had camped on top of a hill, believing the vantage point would provide him with a more advantageous position in terms of observation and a place of attack. The veteran general Wang Ping advised against Ma Su's decision, arguing that their water supply might be cut off and their forces surrounded. While his good counsel was rejected, Ma Su allowed Wang Ping to take 1,000 men and camp nearby the source of the Shu forces' water supply.