The Army of the Potomac was the main Union Army in the Eastern Theater of the American Civil War From 1861 to 1865. The army was also known as Mr. Lincoln's Army due to the close involvement by President Abraham Lincoln. It had two missions. The first was to protect Washington, D.C.. The second mission was to defeat the Confederate Army of Northern Virginia. The generals who led the Army of the Potomac remain some of the most controversial military leaders in history. Under Irvin McDowell, George McClellan, Joseph Hooker and George G. Meade, the army had more defeats than victories.