Xu Xiangqian
Meanwhile, the BSS was playing an active role in suppressing the CCP. Zeng Kuoqing, using his status in the Whampoa Alumni Association, wrote a letter to Xu Jishen (許繼慎), commander of Zhang Guotao's 4th Red Army and a Whampoa graduate, asking Xu to defect to the KMT. Xu did not reply, but when his superiors discovered the letter, suspicions were raised and the CCP decided to carry out a purge. Thousands of commanders and soldiers were tortured and executed, weakening the CCP's resistance. In light of this, in October 1932, Hu Zongnan led his army (mainly commanded by BSS officers) in a cruel and decisive battle against Xu Xiangqian in Hekou Anhui. In contrast to other KMT armies, the army had high-morale, was composed of hand-picked men, and equipped with the best weaponry. With strong support from other armies also led by BSS members such as Yu Jishi (俞濟時) and Huang Jie (黃杰), Xu's CCP army was routed. After suffering some 10,000 casualties, Zhang and Xu retreated. Hu and his troop chased, and when Zhang and his army reached Sichuan to set up another base, Hu remained in Gansu nearby. Hu, with his chosen men and strong army, became known as the King of Northwestern China.