Where did Jews migrate to after the Babylonian conquest?
By the 1st century, Babylonia, to which Jews migrated to after the Babylonian conquest as well as after the Bar Kokhba revolt in 135 CE, already held a speedily growing population of an estimated 1,000,000 Jews, which increased to an estimated 2 million  between the years 200 CE – 500 CE, both by natural growth and by immigration of more Jews from the Land of Israel, making up about 1/6 of the world Jewish population at that era.