A civil war to exterminate the Benjaminites, followed by a mass murder of the residents of Jabeshgilead to give the remaining Benjaminites virgin wives. When that fails to yield enough brides, they kidnap a bunch of girls from another town, which they follow up with another mass rape. Good times!
Following the concubine body part telegram from the last chapter, the tribes of Israel, minus the Benjaminites, gather together with their army of 400 000 men, which puts it on par with Indonesia's current army. The Benjaminites hear about the meeting and ask why they weren't invited. The Levite from the last chapter reminds them about a certain vile incident in Gibeah. He frames it like they stole her, rather than him pushing her out the door. He asks the other Israelites what they think. They want vengeance.
They gather outside Gibeah and start interrogating all the men, demanding the rapists, but the Benjaminites refuse to give them up. Instead, they attack. The total size of the Benjaminite army is 26 000 men, about the same size as a modern army in Scandinavia, including 700 super-special troops, all of whom are left-handed slingshot sharpshooters.
The other tribes ask god who should attack first, and he says Judah. The Benjaminites win the first battle, killing 22 000 Israelites, which is impressive when you consider that the bloodiest battle in the American Civil War, Antitem, only killed 23 000 troops. After that loss, which would take humanity several thousand years to repeat, the Israelites wail and ask god if they really need to wage war against Benjamin. He says yes and a further 18 000 men are killed. The Israelites go to the temple, which, amazingly, is still presided over by Phineas, who must be about 400 by now, and offer sacrifices and prayers to god, who tells them that he's really going to let them win this time. Riiight.
This time, the Israelites succeed in drawing the Benjaminites out of the city and then it's like shooting fish in a barrel. Then they kill everyone in Gibeah, even though only the men sinned. Then they burn the city. The Benjaminites notice the flames, realize they don't have a hope of winning, and flee, but are picked off as they retreat. 25 100 are killed this way, for a 3-day total of 80 100 casualties. 600 Benjaminites do manage to escape to the Rock of Rimmon. The Israelites then slaughter everything in the Benjaminite territory, then institute the first-ever scorched-earth policy, burning everything to the ground. Well, that certainly avenges the gang rape! What happened to those courts Moses was supposed to set up way back in Exodus?
At the initial meeting, the Israelites had pledged not to let their daughters marry any Benjaminites. But then they regret trying to kill all the Benjaminites and ask god what to do, since they've killed all the Benjaminite women. They then discover that one city, Jabeshgilead, didn't send anyone to the meeting. So they decide to kill all the residents save the virgin girls. Unfortunately, there are only 400 of them, and 600 men. Then, fortunately, someone remembers a harvest festival will be taking place soon at Shiloh, and suggests kidnapping some girls from there. As the girls come out to dance, they grab them and run off, caveman style. Sadly, there are no Simeons and Levis this time to avenge the stolen girls.