Koxinga enjoyed a series of military successes in 1651 and 1652 that increased the Qing government's anxiety over the threat he posed. Zheng Zhilong wrote a letter to his son from Beijing, presumably at the request of the Shunzhi Emperor and the Qing government, urging his son to negotiate with the Manchurians. The long series of negotiations between Koxinga and the Qing Dynasty lasted until November 1654. The negotiations ultimately failed. The Qing government then appointed Prince Jidu (son of Jirgalang) to lead an attack on Koxinga's territory after this failure.