General George B. McClellan CDV and Signature with Rank McClellan's military career, though initially promising, was ultimately marked by controversy. A West Point graduate and engineer, McClellan served with distinction during the Mexican-American War. He gained prominence during the Civil War by reorganizing and training the Army of the Potomac, earning the nickname "Young Napoleon". However, his caution and reluctance to engage the enemy, particularly his overestimation of Confederate forces, frustrated President Lincoln. He was removed as General-in-Chief and later as commander of the Army of the Potomac after the Peninsular Campaign and the Battle of Antietam. After the war, McClellan transitioned to politics, running for president against Lincoln in 1864.