 In the days that followed the Union defeat at Bull Run, panicked efforts were made to defend Washington from what was perceived as an imminent Confederate attack.The makeshift trenches and earthworks that resulted were largely confined to Arlington and the direct approaches to Washington.On July 26, 1861, five days after the battle, Maj. Gen. George B. McClellan was named commander of the military district of Washington and the subsequently renamed Army of the Potomac.