Of all the Christian confessions, it has been the Eastern Orthodox Church which has suffered the brunt of persecutions in the 20th century.
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.
Even in the United States, where so many Orthodox have found refuge, the Orthodox Native Americans of the Aleutian Islands were forcibly interned during World War II and many of their churches deliberately destroyed by the U.S. Army.
Unfortunately, the depth and range of the Orthodox suffering throughout the world in this century, remains largely unknown and unappreciated in the West.