When Burnside was replaced as commander of the Army of the Potomac, Hooker was moved up to replace him. In the new assignments resulting from the change, and even though he had little battlefield experience, Sickles was given temporary command of III Corps. But again, the Senate did not confirm his promotion to Major General. Finally, on March 9 (with his rank to date back to November 29), the Senate confirmed his promotion. By the end of March Sickles was officially a major general. Unlike earlier battles, at the Battle of Chancellorsville, Sickles saw action. As Sickles observed Confederate general Stonewall Jackson's flanking maneuver, without orders he pushed forward with two-thirds of his corps to go after the Confederates. This left XI Corps on his right completely isolated. Jackson's confederates then made a crushing attack on XI Corps. Sickles leaving his assigned position was a major factor in the Confederate victory. This started a feud between Hooker and Sickles that continued into the Battle of Gettysburg. Hooker blamed Sickles for the defeat at Chancellorsville.