By mid-1863, Robert E. Lee and his Army of Northern Virginia had humiliated the Union in the battles of Fredericksburg and Chancellorsville. They seemed unbeatable—yet when they met the Union's blue-shirted troops in Gettysburg, Pennsylvania, in July 1863, General Lee was outdone at last. The three-day Battle of Gettysburg was a badly-needed win for the north. But like all victories, it came with a price: This fight went down in history as the Civil War’s bloodiest confrontation. Here’s a short introduction to one of the great turning points in the story of America.

1. BY INVADING PENNSYLVANIA, LEE THOUGHT HE COULD DEMORALIZE THE NORTH.

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In the late spring of 1863, the Union Army had Vicksburg, Mississippi in its sights. With its capture, Union generals hoped to split the Confederacy in half while also asserting control over the lower Mississippi River, a vital transportation route. To keep that from happening, some in the Confederate government wanted to send over reinforcements from the Army of Northern Virginia, but Lee had other ideas.

The general, emboldened by recent victories, mounted an offensive campaign into Pennsylvania. He believed that a strong Confederate presence north of the Mason-Dixon line would pressure the Union into withdrawing some of its soldiers from the Mississippi Delta—and that a huge Confederate invasion would set off a panic in cities like Philadelphia and New York, weakening northern support for the war effort. Lincoln might then lose his 1864 reelection bid, and with Honest Abe out of the White House, the tired north might initiate peace talks. If all had gone well for General Lee, his assault on the Keystone State may have ended the war in the south’s favor. But of course, all did not go well for Lee.

2. THE FIGHT WAS PRECEDED BY AN EXODUS OF BLACK FAMILIES.

On June 12, 1863, Pennsylvania Governor Andrew Curtin put his constituents on high alert. In a statement re-printed by newspapers all over the state, he announced that “information has been obtained by the War Department that a large rebel force, composed of cavalry, artillery, and mounted infantry, has been prepared for the purpose of making a raid into Pennsylvania.”

This news was especially alarming to black families: When Confederate soldiers entered Union territory, they’d often seize African Americans—women, children, and freeborn citizens included—as "contraband." By the end of June, hundreds of black refugees from Gettysburg and other southern Pennsylvania towns had come pouring into Harrisburg, the state’s capital. When Confederates tried to take the city on June 28, black volunteers helped thwart their efforts.

3. ONE MAJOR GENERAL BLAMED THE SHOWDOWN ON A NEED FOR SHOES.

According to Henry Heth, a major general in the Confederate army, he was the one who started the Battle of Gettysburg. Heth said that on July 1, 1863, he sent two brigades into Gettysburg, where they encountered Union resistance, and what began as a minor skirmish mushroomed into a three-day conflict—and a critical victory for the North.

All this begs the question of why Heth dispatched those troops into Gettysburg in the first place, considering he was under strict orders not to go on the offensive. Heth explained his rationale like this: He needed to go shoe shopping. “Hearing that a supply of shoes was to be obtained in Gettysburg,” Heth wrote in 1877, “and greatly needing shoes for my men, [on June 30] I directed General Pettigrew [a brigade commander of his] to go to Gettysburg and get these supplies.” Pettigrew returned with stories that there was cavalry present in Gettysburg, but the commanders believed that this was just an observation detachment and the bulk of the Union army was far away, meaning an assault on Gettysburg would likely succeed. Heth later recalled saying “I will take my division tomorrow and go to Gettysburg and get those shoes!”

Historians think Heth wasn’t being entirely truthful about the matter. Another Confederate division had already gone on a "supply run" through Gettysburg and didn’t obtain many shoes.

While it is generally agreed that Heth did send troops ahead for reconnaissance of the area, and those troops’ interaction with Union soldiers started the battle, historians continue to debate the rest of the specifics. Some propose that Heth was searching for non-shoe supplies, while others propose that Heth was eager to impress Lee and might have used the supplies as an excuse to pick a fight. Still others argue that the roads funneled both armies through Gettysburg, making a showdown inevitable.

4. ALMOST 16,000 MEN DIED ON THE FIRST DAY ALONE …

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At first, the rebels’ odds of scoring a victory in Gettysburg seemed pretty good—the first major clash on July 1 involved 7600 Confederate infantry fighting against just 2748 Union cavalrymen. Later on that day, around 27,000 Confederate soldiers approached from the north and drove 22,000 Union soldiers out of the town, leaving them to reconvene on Cemetery Hill to the south. By nightfall, Lee had lost over 6000 men and around 9000 northerners had been killed in total. Had the fighting ended after that first day, Gettysburg still would have had one of the 20 highest body counts of any battle in the war.

5. … AND YET THERE WAS ONLY ONE CIVILIAN CASUALTY OVERALL.

The Union forces bounced back on July 2 with the arrival of Major General George Meade and most of his army, which brought the total number of northern troops up to 90,000. They were fighting against 75,000 Confederate troops. The battle stretched into July 3, with the Army of Northern Virginia leaving the area the next day. It’s estimated that there were between 46,000 and 51,000 casualties at Gettysburg overall.

Still, just about every innocent bystander who witnessed the carnage lived to tell the tale. Twenty-year-old Mary Virginia Wade (also known as "Jennie" or "Gennie") had the distinction of being the only civilian to die within Gettysburg’s borders during the battle. A resident of the town, she was reportedly hit by a stray bullet that tore through her home as she was baking a loaf of bread. Wade is now commemorated by a statue on Baltimore Street.

6. FEMALE SOLDIERS FOUGHT ON BOTH SIDES.

While the Civil War is generally viewed as a male conflict with the demure women staying behind, that’s not actually true: Hundreds of women—drawn by a sense of adventure, a commitment to the cause, or just the opportunity for a steady income—are thought to have enlisted. Nine verified female soldiers died on a Civil War battlefield, and one of them was killed at Gettysburg. Lying among the corpses of all the southerners who had fallen in Pickett’s charge was the uniformed body of a woman. Another female Confederate soldier took a bullet to one leg, which had to be amputated. It’s known that a third woman fought for the south at Gettysburg as well—and at least two female soldiers saw action there as part of the Union army.

7. GEORGE PICKETT DIDN’T COMMAND ALL OF THE TROOPS IN PICKETT’S CHARGE.

By the third day, the fighting had shifted to the south of Gettysburg proper. The Union troops stood in a fishhook-shaped arrangement that began down at the twin hills of Big and Little Round Top, stretched the length of Cemetery Ridge (a raised geologic feature), and curved around Cemetery Hill. Confederates were moving in from the north and the west.

Lee wanted to strike at the heart of the Union line along Cemetery Ridge. But to get there, his men would have to cross an open field, leaving them exposed to Union artillery fire. Against the advice of his righthand man General James Longstreet, Lee went ahead with the charge. Of the 12,000 Confederate men who were ordered to participate, more than half were killed, captured, or wounded while the Union line remained unbroken (though it suffered heavy losses as well). Remembered today as the “High Watermark of the Confederacy,” this disastrous event was romanticized by southern writers and incorporated into Dixie’s “Lost Cause” narrative. The effort is more formally called “Pickett’s Charge” because one division in the Confederate attack was led by George Pickett, a Major General from Richmond. He would spend the rest of his life nursing a grudge against Robert E. Lee; in Pickett’s own words, “That old man … had my division massacred.”

Posterity may have attached Pickett’s name to the charge, but his division only supplied between 4000 and 6200 of the soldiers who were in it. Accompanying his men were thousands of other troops under the command of James Pettigrew and Isaac Trimble.

8. GEORGE A. CUSTER WAS THERE.

Pickett’s charge is thought to have been one half of a pincer-like assault: While Pettigrew, Trimble, and Pickett himself led their brigades towards Cemetery Ridge, 6000 mounted cavalrymen tried to sneak around it. By doing this, the horsemen could have opened fire on the Union line from the east just as Pickett and company were rushing over from the west. Enter George A. Custer—a graduate of West Point and a Brigadier General in the Union army—who stopped them in their tracks with their own cavaliers. The Confederate riders were eventually driven away, leaving the Union troops on Cemetery Ridge free to mow down Pickett’s charge.

Gettysburg wasn't the only infamous battle Custer would be a part of: In 1876, he and 267 of his cavalrymen were killed by Sioux, Cheyenne, and Arapaho warriors in a Montana valley in the Battle of Little Bighorn.

9. THE WAGON TRAIN OF WOUNDED CONFEDERATES WAS 17 MILES LONG.

Beaten and battered, the Army of Northern Virginia pulled out of Gettysburg on the fourth of July (the same day Ulysses S. Grant finally took Vicksburg). There were enough wounded Confederates to fill a 17-mile wagon train that Lee took back to the South. On its way back to Virginia, the convoy ran into trouble at the Potomac River. The weather had been calm and cloudy throughout the clash at Gettysburg. But on July 4, a heavy rainfall arrived that lasted for several days. So when Lee’s men finally reached the Potomac, high water levels trapped them on the northern side of it.

Lincoln wanted General Meade to grab this opportunity and wipe out the now-cornered Army of Northern Virginia. Meade chose to proceed with caution—in part because his troops were still weary from the action at Gettysburg. Some of his outfits had skirmishes with Lee’s men until the Confederates were finally able to cross the Potomac at Williamsport, Maryland on July 13/14. “Our army held the war in the hollow of their hand and they would not close it,” said a disappointed Lincoln.

10. THE BODY OF ONE FALLEN SOLDIER DIDN’T TURN UP UNTIL 1996.

Once the fighting at Gettysburg subsided, the town’s 2400 residents had to dispose of nearly 7000 human corpses the armies left behind. Shallow, rock-covered graves were hastily dug for the deceased.

After the battle, Governor Curtin lobbied for a Soldier’s National Cemetery to be built at Gettysburg. His request was granted, and the bodies of Union soldiers were reinterred at the chosen burial site, which was formally consecrated on November 19, 1863. President Lincoln attended the ceremony and gave the speech that would come to be known as the Gettysburg Address. The scent of death hung in the air while Abe spoke. That’s because thousands of Confederates were still lying in shoddy graves on the town’s outskirts—attracting flies and vultures. Most remained in situ until southern organizations started digging up fallen Confederates in 1871 so the bodies could receive proper burials.

A few cadavers apparently escaped their notice: In 1996, the body of a Civil War soldier was found near Railroad Cut. Archaeologists couldn’t identify the man, or even determine which side he’d fought for. (It’s been suggested that he was a Mississippi Confederate.)

11. THERE WAS A BIG REUNION IN 1913.

With some help from the U.S. War Department, multiple state legislatures, and a Major League baseball player who had become Pennsylvania’s governor, Gettysburg threw a massive party to commemorate the 50th anniversary of its great battle. The event began on June 29, 1913 and lasted until the sixth of July. Over 50,000 Civil War vets—most of whom were in their seventies—turned up to commemorate the battle. New memorials were dedicated, former enemies took photos together, and President Woodrow Wilson dropped by to give a speech. A highlight was the peaceful reenactment of Pickett’s Charge: 200 men retraced the steps they’d taken half a century prior and then met up on Cemetery Ridge to trade handshakes.