I've recently been reading Robert Kaplan's books on his travels through Eastern Europe. In fact, several of his books provide extensive history of Eastern Europe and the migrations from the Asia which originally populated it, and the Orthodox and Roman Catholic Churches.
Eastern Europe has suffered two devastating occupations: first the Ottoman Empire's invasion and subjugation, then the Nazis and the Communists (which I classify as a continuation of similar totalitarian brutality). The Ottoman occupation was as brutal. Which stands in marked contrast to the brilliance of Attaturk, and the abysmal failure of the 'milder' socialism of today's Europe.
I recommend Kaplan's books to get a sweeping overview. But this article, LarryLied, is a snapshot of a dominant and evil religion (socialism) determined to destroy Western Civilization and its primary religions.