Ottoman rule

When the Ottomans arrived, two Greek migrations occurred. The first migration entailed the Greek intelligentsia migrating to Western Europe and influencing the advent of the Renaissance. The second migration entailed Greeks leaving the plains of the Greek peninsula and resettling in the mountains. The millet system contributed to the ethnic cohesion of Orthodox Greeks by segregating the various peoples within the Ottoman Empire based on religion. The Greek Orthodox Church, an ethno-religious institution, helped the Greeks from all geographical areas of the peninsula (i.e., mountains, plains, and islands) to preserve their ethnic, cultural, and linguistic heritage during the years of Ottoman rule. The Greeks living in the plains during Ottoman occupation were either Christians who dealt with the burdens of foreign rule or Crypto-Christians (Greek Muslims who were secret practitioners of the Greek Orthodox faith). Many Greeks became Crypto-Christians to avoid heavy taxes and at the same time express their identity by maintaining their secret ties to the Greek Orthodox Church. However, Greeks who converted to Islam and were not Crypto-Christians were deemed Turks in the eyes of Orthodox Greeks, even if they didn't adopt Turkish language.