By the next May, there had been some rearrangements in the Army of the Potomac, which was now under the control of Maj. Gen. Joseph Hooker. Hooker placed in command of the XI Corps Maj. Gen. Oliver O. Howard, because the latter had been angry he was passed over for command of the III Corps. Since March 10, McLean had grown popular with the men as commander of the First Division of the XI Corps, but Howard opted to replace him with Brig. Gen. Charles Devens, a New England man very much like Howard; McLean was relegated to brigade commander. As such, he found himself on the right flank of the Union battle line for the Battle of Chancellorsville. This would be the part of the line that Stonewall Jackson attacked with his famous Flank March.