In 537, Gao Huan launched a three pronged attacked on Western Wei. When one column was crushed by a concentration of 6,000 cavalry under Yuwen Tai, Gao retreated. Gao made a second attempt with a force of 100,000. The resulting Battle of Shayuan on 19 November saw Gao's entire force defeated in a surprise ambush by 7,000 heavy cavalry. The eastern army lost more than half its men.