One day, Amaranta, Aureliano José's aunt and the woman who's been raising him, realizes that he's now almost a man. In this novel, that of course means incest.
They've been sleeping in the same bed since Aureliano José was a little boy, but now it's clear that he has the hots for his aunt and she's into it, too. For a while they do… well, it's unclear, but basically everything but actual sex. One day Úrsula almost catches them. Amaranta realizes that she needs to put the kibosh on this disgustingness, and she does.
Meanwhile, the Liberals and the Conservatives are about to negotiate a peace settlement. It'll mean some congressional seats for the Libs, amnesty for the fighters… the usual.
Colonel Aureliano Buendía is not on board with this at all. He takes some of his best men and starts new rebellions all over the country. Aureliano José goes off to war with him.
After a while, Aureliano José leaves Colombia and starts uprisings all over Central America. He's part of a movement that wants to unify all the countries in the region.
Macondo is having a nice little moment in the sun, though. The new mayor, General José Raquel Moncada, is a Conservative, of course, but he's a decent guy who is trying to make the war more humane. He's become BFFs with Colonel Aureliano Buendía through truces and prisoner exchanges. He's a great mayor, and everything is going swell in the city.
One of the good things is the school. Aureliano Segundo and José Arcadio Segundo go there, as does their sister, who is now known as Remedios the Beauty, because she is extremely beautiful. (These people weren't exactly creative with the nicknames.)
Right about this time, Aureliano José comes back, fully determined to marry his aunt Amaranta and get it on with her. At first she's kind of feeling it, but she says no so many times that it becomes easy to say no one final time.
The next visitors to the house are the various women who have visited Colonel Aureliano Buendía in his army tent and become pregnant. He's the best soldier out there, and apparently this is a thing. There are seventeen little Aurelianos, all with his eyes. Úrsula baptizes them all and sends them and their moms on their way.
General Moncada knows that Colonel Aureliano Buendía is about to come storming back into town for the bloodiest, most horrible rebellion yet.
Úrsula and Pilar Ternera both feel that something horrible is about to happen and warn Aureliano José to stay off the street at night. He, of course, ignores them, gets into an argument with a soldier in town, and is shot and killed.
That's one more Buendía down for the count. This is starting to get really sad.
The soldier who killed him is shot in turn, and then things calm down for a little while.
A few months later, though, a thousand of Colonel Aureliano Buendía's troops attack the town. General Moncada is captured.
Úrsula sees her son and knows that Colonel Aureliano Buendía has become a harder, less emotionally connected guy than he was before the war.
First things first, Colonel Buendía cancels all that land-transfer stuff that his brother José Arcadio (II) and his brother's unacknowledged illegitimate son Arcadio were doing.
Second things second, Colonel Buendía holds courts-martial and condemns all the captured officers to death, including General Moncada.
When he goes to visit his friend Moncada before the execution, Moncada curses him out for becoming just as bad as the people against whom he's fighting. Then he passes along a letter and some other stuff for Colonel Buendía to give to Moncada's wife, as they've done many times before.