Li Rusong
By then it had become clear that this was a situation much more serious than something that could be handled by local forces. Thus the Ming Emperor mobilized and dispatched a larger force in January 1593 under the general Li Rusong and Imperial Superintendent Song Yingchang, the former being one of the sons of Ming dynasty's Liaodong military magistrate Li Chengliang and the latter being a bureaucratic officer (Ming military law stipulated that any military officer would have an accompanying bureaucrat appointed by the Imperial Court acting as the general's superior). According to the collection of letters left by Song Yingchang, the strength of the Ming army was around 40,000, composed mostly of garrisons from the north, including around 3,000 men with experience against Japanese pirates under Qi Jiguang. Li wanted a winter campaign as the frozen ground would allow his artillery train to move more easily than it would under the roads turned into mud by the fall rains. On 5 January 1593, Wu Weizhong led an advance force of 3,000 men across the Yalu river into Korea, followed by two battalions of 2,000 men each later the same day. At Uiju, King Sonjo and the Korean court formally welcomed Li and the other Chinese generals to Korea, where strategy was discussed.