1. Robert E. Lee’s “perfect battle” went against all military convention.

Chancellorsville is widely considered Lee’s greatest—and most improbable—victory. Despite being outnumbered by nearly 2-to-1, Lee decided on a risky and highly unusual tactic. He elected to divide his smaller forces—not once, but twice—to take on Hooker’s army, including a daring raid by Thomas “Stonewall” Jackson on the Union general’s right flank. Caught completely unawares, Hooker did not press his advantage, instead falling back to defensive positions before finally retreating across the Rappahannock River.

2. A recent overhaul of the Union Army may have played a role in its defeat.

In January 1863, following the disastrous Union defeat and subsequent retreat from Fredericksburg by Ambrose Burnside, President Abraham Lincoln chose as his new commander Major General Joseph Hooker, one of Burnside’s fiercest critics. Soon after, two other senior Union generals resigned, leaving Hooker short on experienced field officers. When he set about reorganizing and streamlining the unwieldy Army of the Potomac, several of his key decisions backfired on him. He created a centralized cavalry unit—unusual for its time—and named Brigadier General George Stoneman to lead it. Stoneman performed poorly at Chancellorsville, continually failing to slow Lee’s advance. Another Hooker move, the reorganization of the 11th Corps under Major General Oliver Howard and the unpopular and cruel Brigadier General Francis Barlow, proved equally disastrous. The demoralized men of the 11th, many of them immigrants from the Midwest with poor English and little training, were completely unprepared to protect the Union’s right flank from Jackson’s assault and soon retreated, suffering significant casualties in the process.

3. Lee won the battle—but at a high cost.

On the night of May 2, while returning from a reconnaissance mission, Jackson was accidentally shot by his own men, members of the 18th North Carolina Infantry, who had mistaken his group for Union cavalry. Jackson was hit three times—twice in the left arm and once in the right hand—and several of his men were killed by the friendly fire. When Lee learned of Jackson’s injuries, he wrote to his trusted lieutenant, stating that he wished he had been injured in Jackson’s place. After Jackson’s left arm was amputated, he seemed to be recovering well, but he soon developed pneumonia and died eight days after he was shot. Lee was devastated, reportedly saying that in losing Stonewall, he had lost his “right arm.” The death of Jackson, one of the South’s brightest stars and ablest generals, was a crushing blow to the Confederate cause.

4. Stonewall Jackson’s body is buried in two different places.

Following Jackson’s death, his body was transported to Richmond, where it lay in state for several days before his burial in Lexington, Virginia. But not all of the celebrated general made that final journey. Beverly Tucker Lacy, Jackson’s personal chaplain, had been well aware of Jackson’s fervent religious beliefs and arranged a proper burial for his amputated left arm in his family’s nearby cemetery. The following year, marauding Union soldiers reportedly dug up and reburied the limb. For nearly 40 years, the location of Stonewall’s arm remained unmarked, until one of his former officers, a member of the Lacy family, erected a stone monument—the only one in the plot—that reads “Arm of Stonewall Jackson May 3, 1863.” The location has become a pilgrimage site of sorts, drawing thousands of visitors every year.

5. Its 30,764 casualties made Chancellorsville the bloodiest battle in American history—briefly.

Nearly two-thirds of the battle’s casualties occurred on a single day—May 3, which produced more dead and wounded than the entire First Battle of Bull Run (First Manassas). When the war ended in 1865, Chancellorsville ranked as the fourth deadliest clash of the Civil War, surpassed only by the battles at Gettysburg, Chickamauga and Spotsylvania Court House. Lee won the battle, but his 13,000 casualties equaled 22 percent of his fighting force—a number nearly impossible for the Confederacy to replace. When Lincoln learned of the Union’s losses (nearly 17,200 men) he was shocked, as was the rest of the North. Sadly, Chancellorsville maintained its grisly title for only a few short weeks before being eclipsed by the horrific casualties at Gettysburg.

6. Hooker became the latest in a long line of short-lived Union commanders.

By May 7, the last of Hooker’s men, including Stoneman’s cavalry, had withdrawn from Chancellorsville. Almost immediately, fingers began pointing at who should take responsibility for the disastrous defeat. Hooker, like Burnside before him, cast much of the blame on his junior officers, and relieved Stoneman from his command. Several other officers quit in anger or were reassigned, leading to dissension in the Union ranks. To make matter worse, Hooker continued to clash with Lincoln and the army’s general in chief, Henry Halleck. With Lee’s Army of Northern Virginia now moving in on Northern territory, Lincoln was forced to make yet another leadership change. On June 28, just three days before the Battle of Gettysburg began, he accepted Hooker’s resignation and named Major General George Meade to lead the Army of the Potomac. Hooker became the fourth Union general to be relieved from command after losing just one major battle, while Meade, who had performed admirably at both Antietam and Fredericksburg, became the third man to command the army in 1863 alone.

7. “The Red Badge of Courage” is based on Chancellorsville.

Though its author, Stephen Crane, was born nearly six years after the war’s end and did not serve in battle, his novel is widely considered to be one of the most realistic portrayals of the Civil War. The book, which depicts the traumatic wartime experience of an 18-year-old Union private named Henry Fleming, was initially serialized in dozens of periodicals in 1894 and published as a novel the following year. Crane, who was only 24 when the book came out, based the battle scenes and troop movements on those at Chancellorsville, and is believed to have interviewed veterans of the campaign: the men of the 124th New York Volunteer Regiment, a group popularly known as the Orange Blossoms. The book met with mostly positive reviews, but did have its detractors, including former Union officers Alexander McClurg and Ambrose Bierce. Nonetheless, “The Red Badge of Courage” made Crane an overnight sensation; it has remained in print ever since and been adapted for the screen several times. Just a few years later, Crane witnessed the horrors of battle firsthand, serving as a war correspondent during the Spanish-American War and elsewhere. After suffering a series of personal and financial setbacks, he died of tuberculosis at the age of 28.