Caligula declared himself a god and ordered a colossal statue of himself installed inside the Holy of Holies in Jerusalem. The Jews told the Roman general they would rather die, every last one of them, than allow it.
According to Josephus in Antiquities XVIII-XIX, Caligula's madness had been escalating for years. He called himself the brother of Jupiter. He plundered Greek temples and shipped their treasures to Rome. He executed senators to seize their wealth. When a Jewish delegation led by Philo of Alexandria came to protest anti-Jewish riots in Egypt, Caligula mocked them to their faces. Philo walked out and told his companions to take courage, because a man this arrogant had already turned God against himself.
Then Caligula sent Petronius, the governor of Syria, with two legions and orders to erect the imperial statue in the Temple by force if necessary. Petronius marched to Ptolemais and began commissioning the statue. Tens of thousands of Jews descended on his camp. They did not come armed. They came with their families. They told Petronius they would sooner be slaughtered, with their wives and children, than see the Temple desecrated.
Petronius was shaken. He saw an entire nation prepared to die rather than submit. He also noticed that the Jews had stopped planting their fields, which meant famine and the loss of Roman tax revenue. He wrote to Caligula asking for a delay. Agrippa, who was in Rome and had the emperor's ear, threw a lavish banquet for Caligula and used the occasion to beg him to rescind the order. Caligula, in a rare moment of generosity, agreed.
But Caligula then changed his mind and sent new orders commanding Petronius to proceed immediately, adding that Petronius himself should commit suicide for the delay. The letter traveled slowly. Before it arrived, Caligula was assassinated by his own Praetorian Guard in January of 41 CE. Petronius received news of the emperor's death before the suicide order reached him. The Temple was saved by twenty-seven days of favorable winds.