Army of the Potomac
There was an urgency to gathering an army together as quickly as possible. Washington was being threatened by the presence of 20,000 Confederate troops camped just 25 miles away near Manassas, Virginia. During the months of April, May and June of 1861, volunteers were everywhere. Almost daily a new group arrived by train. They camped everywhere, even on the White House lawn.  On May 24, 1861, Brigadier general Irwin McDowell took command of the new army, called the Army of Northeastern Virginia. With training still incomplete McDowell was ordered to engage the Confederate forces at Manassas. He moved south very slowly which allowed the Confederate commander, P. G. T. Beauregard, enough time to call for reinforcements from his fellow general, Joseph E. Johnston. The engagement that followed was called the First Battle of Bull Run.