After the fall of Constantinople, After the fall of Constantinople, Christians under the Ottoman rule experienced a very stressful existence, under slavery conditions. They persevered through that occupation and utilized education as a tool for survival, in exchange for helping the Ottoman Empire expand militarily. To achieve their survival, Greek families employed unparalleled ingenuity, planning, patience and secrecy. Many fled abroad, further spreading Greek civilization and creating secret Greek organizations, geared to mobilize the world against the Ottomans. To defend against that, the Ottomans engineered the total separation of the Orthodox and Catholic Churches, isolating any Christian rebellion from any help from the West. Greeks tried unsuccessfully to find allies in the West but eventually settled into a secret alliance with Russia, which eventually brought about the Greek Revolution of 1821. Their tenacity to preserve faith and culture, withstood centuries of pressure, even when whole societies around them yielded, and were assimilated in the Moslem world.