By 20 May, Li had captured Bengbu, whilst Chiang unleashed a four-pronged attack through Jiangsu, toward the warlord power base in Shandong. He Yingqin led the NRA First Army across the Yangtze at Zhenjiang, and moved to capture Haizhou. On 28 May, Li took Suzhou, while the "Guominjun" took Luoyang, forcing Zhang Zongchang to withdraw his forces to Shandong, and Zhang Xueliang to fall back north of the Yellow River. Following Xueliang's retreat, Feng Yuxiang moved east from Luoyang to Zhengzhou. Finally, on 2 June, the NRA captured the vital railway junction of Xuzhou. With both the Longhai and Beijing–Hankou railways under NRA or "Guominjun" control, Feng came into direct contact with the Wuhan and Nanjing factional governments, who both sought his aid. He met with Wang Jingwei and Tang Shengzhi at Zhengzhou on 10–11 June, then travelled to Xuzhou to meet with Chiang Kai-shek on 19 June. On the next day, Feng announced that he would align with the Nanjing faction and purge communists from the areas under his control, crippling the Wuhan government's plan to push north, upon which Tang returned to Wuhan with his troops. Whilst Chiang intended to push into Shandong, he was thwarted by the arrival of the Japanese Kwantung Army during the course of June, who were ostensibly deployed to protect Japanese citizens in Qingdao. Around this time, Wu Peifu retreated with his remaining forces into Sichuan, where he announced his retirement. On 5 July, NPA general Chen Yi-yen defected to the NRA, but failed to convince his 10,000 soldiers at Qingdao to do likewise.