Army of Northern Virginia 20 and July 21, the Army of the Shenandoah and forces from the District of Harpers Ferry were added. Units from the Army of the Northwest were merged into the Army of the Potomac between March 14 and May 17, 1862. The Army of the Potomac was renamed "Army of Northern Virginia" on March 14. The Army of the Peninsula was merged into it on April 12, 1862. Robert E. Lee's biographer, Douglas S. Freeman, asserts that the army received its final name from Lee when he issued orders assuming command on June 1, 1862. However, Freeman does admit that
Army of Northern Virginia Gen. J. E. Johnston as it was joined by the Army of the Shenandoah on July 20, 1861, when command was relinquished to General J. E. Johnston. The following day this army fought its first major engagement in the First Battle of Manassas. With the merging of the Army of the Shenandoah, Gen. Joseph E. Johnston took command from July 20, 1861, until May 31, 1862. Under the command of Johnston, the Army immediately entered into the First Battle of Manassas. On October 22, 1861, the Department of Northern Virginia was officially created, officially ending the Army of the Potomac.