From newly captured Xi'an, in early April 1645, the Qing forces mounted a campaign against the rich commercial and agricultural region of Jiangnan south of the lower Yangtze River, where in June 1644 the Prince of Fu had established a regime loyal to the Ming. Factional bickering and numerous defections prevented the Southern Ming from mounting an efficient resistance.For examples of the factional struggles that weakened the Hongguang court, see . Some defections are explained in . Several Qing armies swept south, taking the key city of Xuzhou north of the Huai River in early May 1645 and soon converging on Yangzhou, the main city on the Southern Ming's northern line of defence. (taking of Xuzhou; ; converging on Yangzhou). Bravely defended by Shi Kefa, who refused to surrender, Yangzhou fell to Qing artillery on 20 May after a one-week siege.. Dorgon's brother, Dodo, then ordered the slaughter of Yangzhou's entire population.. As intended, this massacre terrorised other Jiangnan cities into surrendering to the Qing Empire. (purpose of the massacre was to terrorise Jiangnan); , passim (late-Qing uses of the Yangzhou massacre). Indeed, Nanjing surrendered without a fight on 16 June after its last defenders made Dodo promise he would not harm the population.. The Qing forces soon captured the Ming emperor (who died in Beijing the following year) and seized Jiangnan's main cities, including Suzhou and Hangzhou; by early July 1645, the frontier between the Qing Empire and the Southern Ming regime had been pushed south to the Qiantang River. (capture of Suzhou and Hangzhou by early July 1645; new frontier); (capture of the emperor around 17 June, and later death in Beijing).
