A detailed account of the battle of Antietam that clarifies the epic struggle Unfurl Those Colors! examines the operational fabric of leadership and command in the Army of the Potomac during one of the most critical campaigns and battles of the Civil War. The Battle of Antietam remains “the bloodiest single day of combat in American history” with over 5,000 killed, 20,000 wounded, and 3,000 missing. Many eminent Civil War historians consider it the turning point of the war. As a result of the perceived Federal success at Antietam, Abraham Lincoln was able to issue the Emancipation Proclamation to make the war about ending slavery and terminating any hope of European recognition for the South. This book constitutes an operational study of the Army of the Potomac during this campaign and battle, carefully documenting the command decisions of army commander George B. McClellan and following the execution of those decisions through the corps level of command and down to the ordinary soldier in the Second Army Corps. It reappraises the leadership and decisions of Edwin V. Sumner during the battle of Antietam as the one federal corps commander who was steadfast in carrying out McClellan’s plan of battle and effectively directed the battle on the Federal right. It details as no previous account has the fighting of the Second Army Corps at Antietam to include Sedgwick’s division in the West Woods and French’s and Richardson’s divisions at Bloody Land.