McDowell was promoted to
brigadier general in the
regular army on May 14, 1861, and was given command of the
Army of Northeastern Virginia on May 27. The promotion was partly because of the influence of his mentor,
Treasury Secretary Salmon P. Chase. Although McDowell knew that his troops were inexperienced and unready and protested that he was a supply officer, not a field commander, pressure from the
Washington politicians forced him to launch a premature offensive against
Confederate forces in
Northern Virginia. His strategy during the
First Battle of Bull Run was imaginative but ambitiously complex, and his troops were not experienced enough to carry it out effectively, resulting in an embarrassing rout. After the defeat at Bull Run,
Major General George B. McClellan was placed in command of the new
Union Army defending Washington, the
Army of the Potomac. McDowell became a division commander in the Army of the Potomac. On March 14, 1862, President Lincoln issued an order forming the army into corps, and McDowell got command of the
I Corps as well as a promotion to major general of volunteers. When the army set off for the Virginia Peninsula in April, McDowell's command was detached for duty in the Rappahannock area out of concern over Stonewall Jackson's activities in the Shenandoah Valley (one division was later sent down to the Peninsula). Eventually, the three independent commands of Generals McDowell,
John C. Frémont, and
Nathaniel P. Banks were combined into Major General
John Pope's Army of Virginia and McDowell led the
III Corps of that army. Because of his actions at
Cedar Mountain, McDowell was eventually brevetted
major general in the regular army; however, he was blamed for the subsequent disaster at
Second Bull Run. McDowell was also widely despised by his own troops, who believed him to be in cahoots with the enemy. He escaped culpability by testifying against Major General
Fitz John Porter, whom Pope
court-martialed for alleged insubordination in that battle. Pope and McDowell did not like each other, but McDowell tolerated serving under him with the full knowledge that he himself would remain a general after the war was over while Pope would revert to the rank of colonel. Despite his formal escape, McDowell received no new assignments for the next two years. ==Later service and postbellum career==