Johnson's "History of the Jews," so far as population. Jews were like today's Muslims: they despised homsexuality and had large, extended families. As for the war, the Emperor Trajan had extended the empire to include Mesopotamia when the Jews in his rear revolted. Took a while for the Romans to regroup. But the Jewish Wars in Palestine saw were some of the worst fighting that the Romans encountered in the history of their empire. After the third, Barkhoba rebellion, the Romans finally crushed Jewsish political ambitions. Thereafter the Jews were immersed in religion and business.
It would seem strange though that a territory as small as Judea, which is not super-fertile to boot (though moreso than some of the surround region) would have such a large popultion.