George McClellan

Abraham Lincoln appointed McClellan the commander of the Army of the Potomac, or the Northern Army. This Union fighting force was different from General Grant's Army, which fought primarily in the South.

McClellan was a cautious commander. He rarely pursued retreating forces, and was comfortable with tradtional fighting tactics. For this reason, he often suffered defeat. Lincoln removed McClellan from his command in 1862 after Antietam.