The Jews of Judea, hoping for a better deal than they had with the Byzantines, fought on the side of the Persians. In 611 CE, Persia conquered Syria and Judea. The army entered Jerusalem with the Jews cheering. They and the Jews slaughtered from 60,000-90,000 Christians. They also destroyed the Holy Sepulchre, built by Helena.
To their dismay, the Jews discovered that the Persians were even crueler and harder to live with than the Christians had been. They immediately tried to work out a deal with the Byzantine emperor Heraclius to help him retake the Holy Land. The emperor agreed to the terms set by the Jews and, in 629 CE, after a bloody war, the Byzantines succeeded in winning back all of the territory which the Persians had conquered eighteen years earlier. Both countries were exhausted financially by the wars. Neither was in very good condition, but Judea was in even worse shape because so much of the fighting had taken place within her borders.
When Heraclius gained control of Judea, the Jews went to him reminding him of his promises. Heraclius, assured by the Christian clergy that it was God's will and that a week of fasting would atone for any possible sins, ordered all Jews killed and all synagogues destroyed. The Jews who didn't get caught and slaughtered at once fled to Egypt and other points north or south.
Heraclius ordered forced conversion for all Jews in the Byzantine Empire, but the order was carried out only in Carthage. Heraclius asked the king of the Franks to kill all Jews, but he refused.
It looked like the end of Judaism in Judea. However, things were going on in the Arabian desert which, within seven years, would change the picture of the Near East and of the whole world.