At Wuhan, Tang Shengzhi began to mobilise his troops for an attack on the Nanjing government. Aware of this threat, Chiang recalled troops from the Shandong border in an effort to block Tang. In turn, the NPA launched an attack on Chiang in early July, reclaiming much of the territory they had lost. By 24 July, the NPA had retaken Xuzhou. In the face of mounting losses inflicted by the warlords, the Wuhan and Nanjing factions began reconciliation talks. The Wuhan government purged communists from its ranks and expelled Soviet advisors, facilitating a rapprochement between the two factions, but also sparking the communist Nanchang uprising, which weakened its authority. In the meantime, however, the NPA counter-offensive continued, reaching Bengbu on 9 August, and forcing Chiang to withdraw his troops south of the Yangtze. In return for his co-operation, Wang Jingwei demanded that Chiang resign from his post of commander-in-chief, and relinquish all political titles. Accordingly, Chiang resigned from his post on 12 August, though this did not immediately reunify the Wuhan and Nanjing factions.