The Union position on Cemetery Ridge on July 3, 1863 at Gettysburg could have been taken out of a military textbook. In fact it was: Dennis Hart Mahan's A Treatise on Field Fortifications. It is a misconception that a steep slope like the one held by the Confederates at Missionary Ridge a few months later is the most defensible. On the right, troops on Cemetery Ridge were protected from dangerous enfilading artillery fire by Cemetery Hill. The gently sloping ground in front of the ridge would disrupt direct artillery fire from the Confederate side, with troops behind the ridge almost completely protected from enemy fire. For the Union artillery, the opposite was true. The gentle sloop in front of the ridge provided clear fields of fire, and as the enemy drew close their lines were enfiladed by Union artillery and musket fire on both flanks. It was a stronger position than Wellington held at Waterloo.
It was a miracle that any Confederates in Pickett's charge were able to cross the killing ground in front of Cemetery Ridge. Yet many did and surged over the stonewall in front a copse of trees that was the focus of the Confederate attack. As other Union regiments fell back, Pennsylvania's Irish 69th Regiment held on in front of the copse of trees. When Confederate General Lewis Armistead led his men over the wall and began turning abandoned artillery on the Union troops, the Irish boys in the 69th shot him down. Soon reinforcements arrived led by Irish-American Colonel James Mallon's 42nd NY "Tammany Hall" Regiment, the Confederates were overwhelmed and threw down their weapons.
No one from the 69th Pennsylvania was awarded a Medal of Honor for valor at Gettysburg. Later the Irish boys remarked: "If we'd have known they were giving awards for capturing Confederate flags, we'd have picked up a few. They were all around us. We were completely exhausted and sat and watched while other boys picked them up."