Antiochus hears about a temple in Elymias in Persia that is filled with treasure, including some relics from his grandfather Alexander the Great. Rather than just ask for the stuff back, or offer to buy it, he of course decides to attack, but the city heard he was coming and has prepared itself. They rebuff the attack and he goes back to Babylon, where he also hears about the defeats in Judea. He goes to bed to grieve and stays there for several days, until people think he's going to die. He calls all his friends together to go over all his regrets in life, chief among them being raiding Jerusalem. He appoints his friend Philip as his heir and regent to his son Antiochus Jr. Then he dies aged 149.
Lysias - who may or may not be Philip, and who may or may not have his own son named Antiochus, sets up someone named Antiochus as the new ruler and changes his name to Eupator. Together they start locking up all the Jews they find near the temple, which causes Judas to decide to besiege Babylon. Or possibly some other place. The bible really underscores the importance of pronouns by its vagueness.
Anyway, there is a siege and some people manage to get to the king and ask him when he's going to avenge the deaths of his citizens and also advise him to give up, given how persistent and murderous these Jews have proven to be. The king gets angry at this and gathers an army of 120 000 men and 32 battle elephants. They head for Bethsura, but the locals fight back and set fire to them. Then Judas shows up, which causes the king to also come in person with even more men. And to the end they might provoke the elephants to fight, they showed them the blood of gapes and mulberries (v. 34). Then they divide the elephants up amongst the armies so that each elephant has 1000 armoured men and 500 horsemen as bodyguards. Each elephant is decked out with a wooden tower containing 32 men, not counting its trainer. Clearly whoever wrote this knew nothing about elephants. When the elephants meet Judas' army, they handily kill 600 of them.
Someone named Eleazar Savaran notices that one of the elephants is bigger than the others and better kitted out, so he surmises that it must be the king's elephant and decides to attack it. He runs towards it in the heat of battle, killing people left and right, until he kills his way to under the elephant, which he stabs in the stomach until it dies and falls on him. Somehow this scares the Jewish army into retreat, so they go back to Jerusalem with Antiochus' forces in hot pursuit. Unfortunately, they have to surrender rather quickly, because they forgot to stock up before they left. For good measure, the king also takes Bethsura and builds a fort.
Somehow, despite Judas surrendering, Antiochus still has to besiege the temple for another seven years. Eventually the food runs out there until only a few starving priests are left.
Around this time, Lysias hears that Philip is back. Another thing the bible could use: structuring words, because I never knew Philip was gone. But apparently Lysias sent him off to Persia and Media on an errand, and now he's back to reclaim the throne. He wants to make peace with the Israelites by letting them live under their own laws. This satisfies the king, and why no one just sat down and had a conversation and worked out their differences years ago is not explained. Antiochus, possibly the son of the other Antiochus, possibly Lysias' son, then goes back to Antiochia, where he finds Philip ruling, even though he was just in Israel.