http://www.serfes.org/orthodox/memoryof.htm
GREEKS
1914 400,000 conscripts perished in forced labor brigades
1922 100,000 massacred or burned alive in Smyrna
1916-1922 350,000 Pontions massacred or killed during forced deportations
1914-1922 900,000 perish from maltreatment, starvation and massacres; total of all other areas of Asia Minor
TOTAL: 1,750,000 Greek Christians martyred 1914-1922
ARMENIANS
1894-1896 300,000 massacred
1915-1916 1,500,000 perish in massacres and forced deportations (with subsidiaries to 1923)
1922 30,000 massacred or burned alive in Smyrna
TOTAL: 1,800,000 Armenian Christians martyred 1894-1923
SYRIANS AND NESTORIANS
1915-1917 100,000 Christians massacred
THE UKRAINIAN HOLOCAUST OF 1932-33
Sixty-five years ago, between seven and twelve million Ukrainians were systematically and deliberately starved to death in Ukraine, the "Bread Basket of Europe".
In the first two decades, there were massacres of Orthodox Greeks, Slavs, and Armenians in the Ottoman empire, culminating in the 1915 genocide of the Armenians in Anatolia and the near destruction of the ancient Assyrian community in Iraq. In 1923, the entire Orthodox population of Asia Minor was forced to leave their homes, bringing to a close a 2000 year Christian presence.
During the Second World War, two groups of Orthodox Christians were especially targeted for genocide by the Nazis and their allies - the Gypsies and the Orthodox Serbs of Bosnia and Croatia, while the population of Greece, Serbia, European Russia, and Ukraine were designated by the Nazis to serve as slave labor for the Third Reich. By special order of Heinrich Himmler (21 April 1942), clergyman from the East (as opposed to their counterparts from Western Europe) were to be used for hard labor.
At the same time the Orthodox suffered in greater proportion to any other Christian group at the hands of the Communists, who sought to completely eliminate religion.
First in Russia and Ukraine, then in Eastern Europe, in Greece during its civil war (1945-49), and in Ethiopia, the Orthodox Church was the principle target for attach, subversion, or destruction.
Finally, the Orthodox of the Middle East have found themselves caught in the crossfire of the conflicts between Muslim and Jew in Israel and the West Bank, and the civil war between Maronites, Muslims, and Palestinians in Lebanon.
Between the tolls exacted from prisons, concentration camps, forced marches and exiles, warfare, famine, and brutal military occupation, it is reasonable to conclude that up to 50 million Orthodox Christians have perished in the first eight decades of the twentieth century.