Article: Hong Taiji's bureaucracy was staffed with many Han Chinese, including many newly surrendered Ming officials. The Manchus' continued dominance was ensured by an ethnic quota for top bureaucratic appointments. Hong Taiji's reign also saw a fundamental change of policy towards his Han Chinese subjects. Nurhaci had treated Han in Liaodong differently according to how much grain they had, those with less than 5 to 7 sin were treated like chattel while those with more than that amount were rewarded with property. Due to a revolt by Han in Liaodong in 1623, Nurhachi, who previously gave concessions to conquered Han subjects in Liaodong, turned against them and ordered that they no longer be trusted; He enacted discriminatory policies and killings against them, while ordering that Han who assimilated to the Jurchen (in Jilin) before 1619 be treated equally as Jurchens were and not like the conquered Han in Liaodong. Hong Taiji instead incorporated them into the Jurchen "nation" as full (if not first-class) citizens, obligated to provide military service. By 1648, less than one-sixth of the bannermen were of Manchu ancestry. This change of policy not only increased Hong Taiji's manpower and reduced his military dependence on banners not under his personal control, it also greatly encouraged other Han Chinese subjects of the Ming dynasty to surrender and accept Jurchen rule when they were defeated militarily. Through these and other measures Hong Taiji was able to centralize power unto the office of the Khan, which in the long run prevented the Jurchen federation from fragmenting after his death.

Question: When did a Han revolt occur?
1623