From Zunyi, Mao led his troops to Loushan Pass, where they faced armed opposition but successfully crossed the river. Chiang flew into the area to lead his armies against Mao, but the Communists outmanoeuvred him and crossed the Jinsha River. Faced with the more difficult task of crossing the Tatu River, they managed it by fighting a battle over the Luding Bridge in May, taking Luding. Marching through the mountain ranges around Ma'anshan, in Moukung, Western Szechuan, they encountered the -strong CPC Fourth Front Army of Zhang Guotao, and together proceeded to Maoerhkai and then Gansu. Zhang and Mao disagreed over what to do; the latter wished to proceed to Shaanxi, while Zhang wanted to retreat east to Tibet or Sikkim, far from the KMT threat. It was agreed that they would go their separate ways, with Zhu De joining Zhang. Mao's forces proceeded north, through hundreds of kilometres of Grasslands, an area of quagmire where they were attacked by Manchu tribesman and where many soldiers succumbed to famine and disease. Finally reaching Shaanxi, they fought off both the KMT and an Islamic cavalry militia before crossing the Min Mountains and Mount Liupan and reaching the Shenshi Soviet; only 7,000-8000 had survived. The Long March cemented Mao's status as the dominant figure in the party. In November 1935, he was named chairman of the Military Commission. From this point onward, Mao was the Communist Party's undisputed leader, even though he would not become party chairman until 1943.