Irish fight Irish in one of the bloodiest days in Irish military history at Marye’s Heights in Fredericksburg, Virginia on December 13, 1862, during the American Civil War. The Union Army’s Irish Brigade, the Fighting 69th, is decimated by the Confederate States Army during multiple efforts to take Marye’s Heights. In his official report Thomas Francis Meagher writes, “of the one thousand and two hundred I led into action, only two hundred and eighty appeared on parade next morning.”

The Battle of Fredericksburg, fought December 11-15, 1862, is one of the largest and deadliest of the war. It features the first major opposed river crossing in American military history. Union and Confederate troops fight in the streets of Fredericksburg, the war’s first urban combat. And with nearly 200,000 combatants, no other Civil War battle features a larger concentration of soldiers.

Major General Ambrose Burnside’s plan at Fredericksburg is to use the nearly 60,000 men in Major General William B. Franklin’s Left Grand Division to crush General Robert E. Lee’s southern flank on Prospect Hill while the rest of his army holds Lt. Gen. James Longstreet and the Confederate First Corps in position at Marye’s Heights.

The Union army’s main assault against Lt. Gen. Thomas J. “Stonewall” Jackson produces initial success and holds the promise of destroying the Confederate right, but lack of reinforcements and Jackson’s powerful counterattack stymies the effort. Both sides suffer heavy losses (totaling 9,000 in killed, wounded and missing) with no real change in the strategic situation.

In the meantime, Burnside’s “diversion” against veteran Confederate soldiers behind a stone wall produces a similar number of casualties but most of these are suffered by the Union troops. Wave after wave of Federal soldiers march forth to take the heights, but each is met with devastating rifle and artillery fire from the nearly impregnable Confederate positions.

As darkness falls on a battlefield strewn with dead and wounded, it is abundantly clear that a signal Confederate victory is at hand. The Army of the Potomac has suffered nearly 12,600 casualties, nearly two-thirds of them in front of Marye’s Heights. By comparison, Lee’s army has suffered some 5,300 losses. Lee, watching the great Confederate victory unfolding from his hilltop command post exclaims, “It is well that war is so terrible, or we should grow too fond of it.”

Roughly six weeks after the Battle of Fredericksburg, President Abraham Lincoln removes Burnside from command of the Army of the Potomac.