In 200 CE, war broke out between Cao Cao and the northern warlord Yuan Shao. At the Battle of Boma, Xun You suggested that Cao Cao use a diversionary tactic to eliminate Yuan Shao's general Yan Liang; the battle ended with victory for Cao Cao and Yan Liang's death at the hands of Guan Yu. After the victory at Boma, Cao Cao and his forces headed west with their baggage train along the south banks of the Yellow River. Yuan Shao sent his troops across the river to raid the baggage train and they encountered Cao Cao. Cao Cao's subordinates were shocked and they asked him to head back to protect his camp. Xun You said, "This is an opportunity to capture the enemy! Why should we retreat?" Cao Cao looked at Xun You and laughed. He then ordered his troops to use their baggage as bait to lure Yuan Shao's forces into a trap. At the Battle of Yan Ford, when Yuan Shao's soldiers were scrambling for the baggage, Cao Cao sent his infantry and cavalry forces to attack them and scored a major victory; Yuan Shao's general Wen Chou was killed in action. Cao Cao then retreated to Guandu (官渡; northeast of present-day Zhongmu County, Henan); Yuan Shao laid siege to Guandu.