Begin had been a longtime rival of Labor and its leader David Ben-Gurion, the first Prime Minister of Israel (see also: Deir Yassin massacre). This has been claimed to have resulted in Israeli society becoming more religious and traditionalistic, with Haredi Judaism and Religious Zionism playing a bigger role. It also gave rise to the political mobilization of the Mizrahi Jews, who had migrated from the rest of the Middle East following Jewish exodus from Arab and Muslim countries after the 1947–1949 Palestine war which gave rise to Israeli independence.