facing this christian religion which spread by roman influence and power, stood the religion of persia supported by the moral power of india and the far east. the civilization of egypt, extending to phoenicia and that of mesopotamia had for many ages separated the east from the west and prevented any grave confrontation of their ideologies and civilizations. the entry of egypt and phoenicia into christianity dissolved this barrier and brought the christianity of the west and the zoroastrianism of the east face to face. for centuries east and west confronted each other without intermingling between their religions. each felt such fear of the other party's religion that a moral barrier came to replace the old barrier provided by the ancient near eastern civilizations. each was thus compelled to direct its religious expansion to its own hinterland, away from the other's territory. despite the numerous wars they fought, each exhausted its power without being able to confront the other on the religious or civilizational level. although persia conquered and ruled syria and egypt and the approaches of byzantium, its kings never thought of spreading their religion or of converting the christians. on the contrary, the conquerors respected the religions of the conquered and assisted them in reconstructing the temples which war had ravished. they granted them the liberty of upholding their religious rituals. the farthest the persians had gone in infringing on their subjects' religion was to seize the "holy cross" and to keep it in persia. when the tables were turned and the byzantines won, they took the cross back. thus the spiritual conquests of the west were restricted to the west, and those of the east were restricted to the east. the moral barrier separated them as decisively as the geographic civilizational one had done. spiritually speaking, the two paths were equivalent and their equivalence prevented any clash between them.