The Babylonian Jews wanted to fight in common cause with their Judean brethren against Vespasian; but it was not until the Romans waged war under Trajan against Parthia that they acted. To a large extent, the revolt of the Babylonian Jews meant that the Romans did not become masters of Babylonia. Philo speaks of the large number of Jews resident in that country, a population which was no doubt considerably swelled by new immigrants after the destruction of Jerusalem.