Short answers, pulled from the story.
The Army of Virginia was a Union army organized on the 26th of June 1862 under Major General John Pope. It was formed from four existing departments operating in Virginia and had over 50,000 men in its three original corps. It operated for less than three months before being merged into the Army of the Potomac on the 12th of September 1862.
Major General John Pope commanded the Army of Virginia from its creation on the 26th of June 1862 until it was dissolved on the 12th of September 1862. The three corps under him were led by Franz Sigel, Nathaniel P. Banks, and Irvin McDowell.
The Army of Virginia fought at the Battle of Cedar Mountain, the Second Battle of Bull Run, and the Battle of Chantilly. At Cedar Mountain, Banks's II Corps gained an initial advantage before being repulsed by a Confederate counterattack led by A.P. Hill. At the Second Battle of Bull Run, Jackson, Longstreet, and Lee defeated the entire army.
Radical Republicans in Congress and the Cabinet viewed the Army of Virginia as taking the lead in widening the goals of the war. Its senior officers were stronger advocates of abolishing slavery than those in the Army of the Potomac, and the army had a smaller proportion of West Point graduates.
The Army of Virginia had a smaller proportion of West Point graduates than the contemporary Army of the Potomac and its senior officers were more committed advocates of abolishing slavery. Politically, it was seen by Radical Republicans as a force aligned with the broader goal of dismantling the Southern way of life.
The Army of Virginia was merged into the Army of the Potomac on the 12th of September 1862, following its defeat at the Second Battle of Bull Run. Its corps were redesignated: the I Corps became the XI Corps, the II Corps became the XII Corps, and the III Corps reverted to the I Corps designation.