In need of a victory to support the preliminary Emancipation Proclamation, President Abraham Lincoln appointed Maj. Gen. Ambrose Burnside to command of the Army of the Potomac in November 1862. Burnside moved his command to Fredericksburg in anticipation of marching on Richmond. Gen. Robert E. Lee and the Army of Northern Virginia countered, blocking Burnside's path. Without any viable alternatives, Burnside decided to punch his way through. The result was the worst defeat inflicted upon the Union army during the Civil War.