 From the 1st and 2nd centuries Syriac Christianity became the primary religion, while other groups practiced Mandaeism, Judaism, Manichaeism, Zoroastrianism, and the ancient Assyro-Babylonian Mesopotamian religion.Assyrian Christians were probably the most numerous group in the province.The old Mesopotamian religion of the indigenous Assyrians and Babylonians remained strong in places, particularly in the north, in Assyria proper.