The battle of Sharpsburg or Antietam was General Robert E. Lee's first invasion of the North and culminated in America’s bloodiest single day of war and after twelve hours of fighting, over 23,000 troops were killed, wounded, or missing.

Two of Major Gen. Edwin Sumner’s three divisions inexplicable turned south during the II Corps advance and engaged the confederates on the sunken roadway to begin the second phase of the battle of Sharpsburg. The Irish Brigade gained an advantage where now is located the observation tower and enfiladed Rode’s Brigade and the center of the Confederate line was in danger of being overrun but Major General McClellan “lost his nerve”, failed to assign more troops, neglected to exploit the breech, and lost the opportunity to destroy Lee's Army of Northern Virginia.

the War
Between
the States

Sharpsburg
Antietam

September 17^th, 1862

Brig. General William French’s Third Division advanced over the Roulette Farm to attack Brig. Gen. Robert E. Rode’s Brigade of Major General D. H. Hill’s Division of Maj. Gen. Longstreet’s command.

General Rode’s Brigade was positioned in this section of the Sunken Roadway. With the attack of the First and Third Division of the II Corps the confederate position was in danger of being overrun by federals and Rode’s Brigade launched a furious attack.

On the right of the observation tower the sunken road veered to the right,  Brig. Gen. George B. Anderson’s brigade was along that section of the sunken road, and Anderson's brigade was attacked by Maj. Gen. Israel B. Richardson’s First Division of the II Corps. Gen. Richardson was mortally wounded by a shell fragment and although the wound was not considered life-threatening: infection and then pneumonia ensued and Gen. Richardson became one of six generals killed at Antietam.

The Irish Brigade was one of three infantry brigades of Richardson’s First Division of the II Corps, advanced within 300 paces of Gen. Anderson's Brigade and after several volleys, the brigade fixed bayonets and drove the confederates from the sunken road.