6 Deadliest Battles of the American Civil War

The American Civil War, fought from 1861 to 1865, was marked by numerous bloody battles that resulted in substantial casualties. The conflict, primarily over states’ rights and the issue of slavery, saw the Union (the North) and the Confederacy (the South) engage in a series of engagements that would ultimately shape the course of our history.

In the article below, American historians at WHE explore some of the deadliest battles of the Civil War, examining their causes, the combat itself, and their impact on the overall war effort.

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Battle of Gettysburg (July 1-3, 1863)

The Battle of Gettysburg is often cited as the turning point of the Civil War. Fought over three days in Pennsylvania, it resulted in approximately 51,000 casualties, making it the deadliest battle of the war.

The battle commenced when Confederate General Robert E. Lee’s Army of Northern Virginia engaged Union forces under Major General George G. Meade’s Army of the Potomac.

Lee had invaded the North hoping to relieve pressure on Virginia’s farmlands during the growing season, sway public opinion in the North against the war, and possibly gain recognition and aid from European powers for the Confederacy.

On the first day, Confederate forces pushed Union defenders through the town of Gettysburg but were unable to secure Cemetery Hill and Culp’s Hill, critical positions on the Union right flank.

The second day saw fierce fighting at locations such as Little Round Top, the Wheatfield, and Devil’s Den. The Union’s left flank held under severe pressure, thanks in part to heroic stands by regiments like the 20th Maine.

The third day included Pickett’s Charge, a massive Confederate assault on the Union center at Cemetery Ridge. The charge was repelled, resulting in massive Confederate casualties and marking the end of Lee’s campaign into the North.

The Union victory at Gettysburg halted Lee’s invasion and had significant strategic implications, bolstering Northern morale and solidifying Union resolve to continue the fight.

The Battle of Gettysburg (July 1-3, 1863) was undoubtedly the deadliest battle of the Civil War with about 51,000 casualties. Union and Confederate forces clashed in Gettysburg, Pennsylvania, resulting in a pivotal Union victory that turned the tide of the war against the Confederates. Image: An illustration of this battle by US’ illustrator Thure de Thulstrup.

Battle of Chickamauga (September 19-20, 1863)

The Battle of Chickamauga was the second deadliest battle of the Civil War, with around 34,000 casualties. Fought in Georgia, it was a major Confederate victory that temporarily reversed Union gains in the region. Union Major General William Rosecrans faced Confederate General Braxton Bragg in a battle that involved a series of tactical missteps and fierce combat.

Rosecrans’s attempt to maneuver Bragg out of Chattanooga ended with the Union Army fragmented and vulnerable. Bragg, seizing the opportunity, attacked the isolated Union corps with reinforcements, including troops from Virginia under James Longstreet. The battle was marked by its confusion and the wooded, rugged terrain, which frequently resulted in units blundering into each other at close range.

Despite initial Union success, a gap inadvertently created in their line was exploited by a Confederate assault, driving much of the Union force into a disorderly retreat. However, a stout defense by General George H. Thomas at Snodgrass Hill prevented a complete rout, earning him the nickname “Rock of Chickamauga.”

The Battle of Chickamauga (September 19-20, 1863) marked the second deadliest battle, it resulted in approximately 34,000 casualties. Fought in Georgia, this Confederate victory failed to yield strategic advantage. Image: Illustration of the Chickamauga battle by US publishers Kurz and Allison. 

Battle of Spotsylvania Court House (May 8-21, 1864)

Part of Ulysses S. Grant’s Overland Campaign, the Battle of Spotsylvania Court House was characterized by some of the most gruesome combat of the Civil War, including the battle at the “Bloody Angle,” a prolonged and intense melee during a pouring rain.

Lasting for nearly two weeks, the battle was marked by near-continuous combat and high losses on both sides, totaling about 30,000 casualties. Grant’s strategy involved engaging Lee’s forces continuously to exploit the Union’s numerical superiority, gradually wearing down the Confederate capacity for warfare.

The Battle of Spotsylvania Court House, part of the Overland Campaign, spanned from May 8-21, 1864, and was characterized by continuous, brutal combat. It produced about 30,000 casualties, underlining the war’s attritional nature as Union forces under Grant pushed against Lee’s Confederate army. Image: Illustration by Thure de Thulstrup.

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Battle of Shiloh (April 6-7, 1862)

The Battle of Shiloh, also known as the Battle of Pittsburg Landing, was one of the early large battles in the Western Theater, occurring in southwestern Tennessee.

Under the command of Major General Ulysses S. Grant, Union forces were taken by surprise by Confederate forces led by Generals Albert Sidney Johnston and P.G.T. Beauregard.

Despite severe initial setbacks and the death of Johnston, Union reinforcements arrived overnight, allowing Grant to launch a counteroffensive on the second day.

With nearly 24,000 casualties, Shiloh shocked both the North and South by its unexpected ferocity and high number of casualties, underscoring the war’s potential length and severity.

Image: Battle of Shiloh by Thure de Thulstrup.

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Battle of Chancellorsville (April 30-May 6, 1863)

Known for General Robert E. Lee’s most audacious tactics, the Battle of Chancellorsville is often considered his greatest victory, achieved despite being heavily outnumbered.

Lee divided his forces, sending Stonewall Jackson on a flanking maneuver that caught the Union Army under Major General Joseph Hooker off guard.

The victory, however, came at a great cost, including the death of Jackson from friendly fire, which was a severe blow to Confederate morale and military capabilities. The battle resulted in approximately 24,000 casualties.

Image: An artwork, by American publishers Kurz and Allison, depicting the Battle of Chancellorsville.

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Battle of Antietam (September 17, 1862)

The Battle of Antietam, also known as the Battle of Sharpsburg, remains the single bloodiest day in American military history, with about 23,000 casualties. It occurred near Sharpsburg, Maryland, and Antietam Creek, and was the culmination of Lee’s first invasion of the North.

Though technically a draw, the Union halted Lee’s advance, giving President Abraham Lincoln the confidence to announce his preliminary Emancipation Proclamation, which declared the freedom of slaves in Confederate-held territory.

The Battle of Antietam on September 17, 1862, though shorter in duration, was the single bloodiest day in American military history, with around 23,000 casualties in just 12 hours. This battle crucially influenced international perceptions and led to the issuance of the Emancipation Proclamation. Image: A depiction of the Battle of Antietam.

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These battles were not just noteworthy for their high casualties but also for how they influenced the strategic direction of the Civil War.

The Union victories at Gettysburg and Antietam were pivotal, bolstering Northern morale and fortifying the Union’s strategic position.

Conversely, the losses at Chickamauga and Chancellorsville, although costly, demonstrated the Confederacy’s resilience and tactical superiority under capable leaders like Lee and Jackson.

Yet, the attritional strategy adopted by Grant in battles like Spotsylvania reflected a turning point in the war, emphasizing the Union’s advantage in resources and manpower, which eventually led to the Confederacy’s surrender in 1865.

These battles, therefore, illustrate not only the tragic human cost of the war but also the complex military strategies that both sides employed in their quest for victory.

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