Caligula’s Assault on Camp Jupiter is a series of attacks on Camp Jupiter by Caligula. The first wave of the attack, which happened during a new moon was fended off by the Roman demigods and legacies, with additional help from Leo Valdez. However, their camp was in ruins and they suffered heavy casualties. When Caligula heard that his assault had failed, he ordered a second one and headed to the camp himself.
The attack is forewarned by Meg McCaffrey through the Oracle of Trophonius. When they learn that the attack will take place in five days, on new moon, Leo Valdez volunteers to fly to San Francisco on Festus to warn them.
In Apollo's dream, Python tells Nero that he was aware that Camp Jupiter had been warned of the attack. While the assault is not shown, Caligula receives news from Flange, the Pandos, that the attack failed, kills him and orders his ships to sail north to the Bay Area.
Later, Leo and Festus arrive at a private airfield in Santa Monica and tell Apollo, Meg, Piper McLean and the Hedges about the attack. He says that the Romans suffered heavy losses and the camp suffered a lot of damage. However, he mentions that some of the survivors are Frank Zhang, Reyna Ramírez-Arellano and Hazel Levesque.
Frank Zhang recounts the battle with Apollo, saying that hundreds of monsters and the undead attacked them. They only stopped when they reached the Little Tiber, as the dead are deterred by fresh water. He says that some of their dead are missing and that they fear they will be turned on the legion.
The second wave of the assault is referred to as the Battle of San Francisco Bay.