 After the capture of Nanjing in 1645, Zheng accepted an offer to serve as commander-in-chief of the imperial forces and was ordered to defend the newly established capital in Fuzhou under the Prince of Tang.In 1646, Zheng decided to defect to the Manchus leaving the passes of Zhejiang unguarded, allowing Manchu forces to capture Fuzhou.His defection was facilitated by Tong Guozhen and Tong Guoqi.