Banks's division technically belonged to George McClellan despite serving as an independent command in the Shenandoah Valley. On March 14, 1862, President Lincoln issued an executive order forming all troops in McClellan's department into corps. Banks thus became a corps commander, in charge of his own former division, now commanded by Brig. Gen Alpheus Williams, and the division of Brig. Gen James Shields, which was added to Banks's command. After Stonewall Jackson was turned back at the First Battle of Kernstown on March 23, Banks was instead ordered to pursue Jackson up the valley, to prevent him from reinforcing the defenses of Richmond. When Banks's men reached the southern Valley at the end of a difficult supply line, the president recalled them to Strasburg, at the northern end. Jackson then marched rapidly down the adjacent Luray Valley, and encountered some of Banks' forces in the Battle of Front Royal on May 23. This prompted Banks to withdraw to Winchester, where Jackson again attacked on May 25. The Union forces were poorly arrayed in defense, and retreated in disorder across the Potomac River and back into Maryland. An attempt to capture Jackson's forces in a pincer movement (with forces led by John Frémont and Irvin McDowell) failed, and Jackson was able to reinforce Richmond. Banks was criticized for mishandling his troops and performing inadequate reconnaissance in the campaign, while his political allies sought to pin the blame for the debacle on the War Department.