Western identity was defined by Christianity before and during its global conquest.

Evidence

Catholicism and Protestantism. Western Christianity, first Catholicism and then Catholicism and Protestantism, is historically the single most important characteristic of Western civilization. During most of its first millennium, indeed, what is now known as Western civilization was called Western Christendom; there existed a well-developed sense of community among Western Christian peoples that they were distinct from Turks, Moors, Byzantines, and others; and it was for God as well as gold that Westerners went out to conquer the world in the sixteenth century. — Samuel P. Huntington, The Clash of Civilizations and the…, 186