In 1631, Leslie organized English and Scottish troops raised for the Swedish army by James Hamilton, 1st Duke of Hamilton, then the 3rd Marquis of Hamilton, and was promoted Major-General. Leslie was badly wounded in February 1632 near Hamburg. Despite his injury, Leslie was present at the Battle of Lützen (1632). He was appointed Sweden's 13th Field Marshal in 1636 and was one of the Swedish commanders at the Battle of Wittstock in that same year. The overall commander, however, is said by some Swedish historians to have been Johan Banér; but at the time the two commanders had held equal rank: Baner commanding the Swedish Crown Army and Leslie commanding the Army of the Weser. The spectacular victory, however, was largely the work of Leslie and his subordinate, a fellow Scotsman, Lieutenant-General James King, a fact related by Banér himself in his report of the battle to Axel Oxenstierna and the other contemporary reports of the battle.