In late June 1904, while scouting the Japanese positions at Liaoyang, he was shot in the leg, shattering the shin. After less than two months, he returned to active service, without fully recovering from his wounds. In the Battle of Mukden, Rennenkampf again distinguished himself commanding the Tsinghechensky detachment, which was stationed at the left flank of the 1st Manchurian Army led by General Nikolai Linevich. During the battle, he showed great persistence, which combined with other reinforcements, was able to repulse Field Marshal Kawmura's offensive.