September 17, 1862, was the bloodiest day in U.S. military history. More than 125,000 troops faced off and over 24,000 were killed, wounded or missing as Union forces stopped the first Confederate invasion of the North. The 2nd, 6th and 7th Wisconsin Infantry regiments were in the thickest of the fighting. The 6th Infantry led a charge that killed or wounded 150 of its 280 men. Of the 800 officers and men in the Iron Brigade who marched out that morning, 343 were wounded or killed.