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 In July 1864, McDowell was given command of the Department of the Pacific. He later commanded the Department of California from July 27, 1865, to March 31, 1868; briefly commanded the Fourth Military Department; then commanded the Department of the East from July 16, 1868, to December 16, 1872. On November 25, 1872, he was promoted to major general. On December 16, 1872, McDowell succeeded General George G. Meade as commander of the Military Division of the South, and remained until June 30, 1876. From July 1, 1876, he was commander of the Division of the Pacific. In 1882, Congress imposed a mandatory retirement age of 64 for military officers, and McDowell retired on October 14 of that year. In 1879, when a board of review commissioned by President Rutherford B. Hayes