Chamberlain and his men are resting, before being interrupted by cannon fire. Chamberlain holds off on giving orders until a courier arrives from Vincent.
Chamberlain gets ready and wakes Tom, who was still sleeping. He prepares the regiment and they wait. Meade wants this to be a big effort—everyone's getting called into combat.
Vincent arrives and marches the men off. They learn that General Sickles has exposed his troops to the Rebels and is now getting flanked.
A shell explodes nearby, and Chamberlain sends Tom to the back of the column so that they won't both get killed.
Vincent explains that Sickles—famous for shooting and killing his wife's lover—didn't like the ground he was on and foolishly marched his troops down into an exposed position.
The men continue until they get to Little Round Top, which they're supposed to guard. They're the extreme left flank of the army—the end of the line.
Vincent leaves Chamberlain, after telling him that he needs to defend this spot to "the last." Chamberlain wonders what this means—the last man?
The soldiers start building a stone wall to defend their position. They're on a spur sticking out from the rest of the hill.
Chamberlain doesn't like the feeling of being the exposed flank of the army. He sends a company from his regiment—Company B—to go out farther and alert them by shooting if the Confederates attack.
Chamberlain goes up to look out from Little Round Top, along with a colonel from New York. He observes the Confederates as they move closer, and it turns out the Confederates are heading right for them.
Chamberlain heads back to his regiment, where Estabrook finds him. Estabrook implies that he won't be able to look after the six remaining mutineers during the battle. Three of the mutineers agree to fight with Chamberlain, but the others remain stubborn. Chamberlain can't understand this; he won't guard them, but he expects them to remain where they are.
The Union soldiers brace themselves for the assault. Chamberlain advises two men who are standing instead of lying down to find a thicker tree to stand behind.
The Confederates cry the Rebel Yell as they approach. Chamberlain wonders if he'll die and see God.
Firing starts, and soon Chamberlain can see the Confederates, yelling as they charge.
But the 20th Maine is in a good position, dug in. Chamberlain sees lots of Confederates falling.
Crouching and moving, Chamberlain sees many of his own men dead, including one of the prisoners from the Second Maine who just volunteered.
In the next Confederate onslaught, Kilrain suffers a bullet wound to the side. Chamberlain tells Tom to find the surgeon.
From a boulder, Chamberlain can see even more Confederates coming, trying to flank the Union soldiers to the left.
Chamberlain gets hit by a bullet in the hip. Though it's just a nick and there's no blood, he falls off the boulder.
Chamberlain realizes he needs to move his men to prevent the flank. He orders his men to move part of the line to fend off the Confederate advance.
The Confederates attack again, but the stone wall protects Chamberlain's troops. Kilrain seems to be doing okay—he's still firing—though he complains that he doesn't have any alcohol.
In the next attack, Chamberlain shoots a Confederate who's about to kill him. The Union soldiers still holding up, but ammo's getting low.
The Confederates keep attacking. In the next charge, they come in from right, left, and center. Colonel Vincent dies in the process.
In yet another Confederate attack, Chamberlain shoots an officer. At this point, many of the 20th Maine's men are either wounded or dead. Chamberlain says to use their ammo.
Chamberlain uses his brother, Tom, to plug a hole in the line. He wonders what his mother would think.
Over a third of Chamberlain's men are now wounded or dead, and ammo is seriously low. Some of the men want to pull out, but Chamberlain knows that would collapse the whole Union flank. Instead, he orders his men to fix bayonets and get ready to charge.
Chamberlain orders his men to move like a closing door, sweeping the Confederates off the hill. As he leads the charge, screaming, his men drive the Confederates back. Taking out his saber, Chamberlain takes a Southern officer prisoner.
Chamberlain's men chase the Confederates all the way into the valley, before Chamberlain orders them to come back.
Morril's Company B moved out so far that they still had ammunition and were able to fire on the Confederates, driving them back in the last part of the attack. They take plenty of prisoners, including an Alabama officer captured by Tom.
Chamberlain finds Kilrain, who's bleeding: he's been shot twice, but he seems to be doing all right. Chamberlain senses that Kilrain is proud of him, while the older man jokes about how he was shot in the armpit of all places.
Kilrain asks Chamberlain for a drink. Chamberlain goes off to get one, but before he does, Kilrain tells him he's never served under a better man. He shot a soldier who was aiming at Chamberlain at one point.
As it starts to get dark, Chamberlain walks past the wounded and dead. He gives a promotion to a dying soldier.
Chamberlain comes across a teary-eyed Ellis Spear and shares a swig of booze with him.
Tom tells Chamberlain that they fought off four Rebel regiments—around two thousand men—and took around five hundred prisoners.
Colonel Rice, head of a New York regiment, compliments Chamberlain on his charge. Chamberlain hadn't realized that he'd done something unusual.
Rice says that one of the generals wants them to go up on the nearby wooded hill (Big Round Top) and make sure it's secure. Chamberlain agrees.
Tom reports the casualties: forty or fifty dead and ninety wounded—that's about half the regiment. But Chamberlain feels pleased with the job they've done.
Chamberlain finally learns the name of the place—Little Round Top.
Chamberlain goes and says goodbye to Kilrain, who's going to the army hospital tents. They shake hands, and Chamberlain says he'll come see Kilrain tomorrow.
As Chamberlain walks up the other hill, he looks at his men and feels joy. He's happy about the victory.