After Bar Kamtza's betrayal, the emperor sent Nero to conquer Jerusalem. According to Gittin 56a, Nero arrived and performed a series of divination tests. He shot arrows in every direction—east, west, north, south. Every arrow fell on Jerusalem. The city was marked for destruction.
Nero then asked a passing child to recite the verse he had learned that day. The child quoted (Ezekiel 25:14): "And I will lay My vengeance upon Edom by the hand of My people Israel." Nero understood: God intended to use Rome as His instrument of punishment—and then punish Rome in return. Nero fled. He converted to Judaism. According to the Talmud, Rabbi Meir was a descendant of Nero.
Rome then sent Vespasian. He laid siege to Jerusalem for three years. Inside the walls, the zealots burned the city's food stores to force the people to fight rather than negotiate. Rabban Yohanan ben Zakkai, smuggled out in a coffin, appeared before Vespasian and greeted him as king.
Vespasian protested: "I am not a king." Rabban Yohanan answered: "You must be, because the prophet says Jerusalem will fall only to a king—'And the Lebanon shall fall by a mighty one' (Isaiah 10:34), and 'Lebanon' is the Temple, and 'mighty one' is a king."
At that moment, a messenger arrived from Rome. The emperor was dead. Vespasian had been named his successor. He tried to put on his other shoe, but his foot had swollen. Rabban Yohanan explained: "Good tidings make the bone fat" (Proverbs 15:30). The remedy? Bring someone displeasing before you, because "a broken spirit dries the bones" (Proverbs 17:22). Vespasian did so, and the shoe fit.
Before leaving for Rome, Vespasian told Rabban Yohanan: "Make a request." Rabban Yohanan asked for Yavneh and its Sages—a small academy town instead of Jerusalem. The Temple was lost. The Talmud was born.