The main fighting initially centered around Urumchi, which Hui forces laid under siege until Sheng Shicai's troops were reinforced by White Russian and Manchurian soldiers who had previously fled the Japanese invasion of northeast China. In April 1933, Jin was deposed by a combination of these forces and succeeded by Sheng, who enjoyed Soviet support. Newly bolstered, Sheng split the opposing forces around Urumchi by offering several Uyghur commanders (led by Xoja Niyaz Hajji, an advisor to the recently deceased Hami khan) positions of power in southern Xinjiang if they would agree to turn against the Hui armies in the north, led by Ma Zhongying (馬仲英).