Michael Shermer’s Skeptic Society has an interesting article up based on And God Created Lenin: Marxism vs Religion In Russia, 1917-1929, which chronicles the futile attempt by the Communists to exterminate religion. One must make a distinction here between religion and a specific religious system and organization.
In The Rise of Western Christendom by Peter Brown I was struck by two simultaneous processes as the Roman Empire withdrew from portions of Germany and Britain and the barbarians rushed in. First, there is the archaeological record of the persistence of folk Christianity for centuries (e.g., amongst the presumably post-Roman peasant subjects of the Avars, or the British remnant under pagan Anglo-Saxon rule). But second, there is the almost invariable creeping advance of doctrinal deviation and religious syncretism once the institutional “police” disappear from the scene. This was in clear evidence in portions of Germany which came under Carlognian direct rule after a long period of Merovingian neglect. St. Boniface records nominally Christian priests regularly taking part in pagan cults and garbling the most basic professions of their faith. A more recent example are the Kakure Kirishitan, Japanese “Hidden Christians” who reemerged after the opening of their nation to the West during the 19th century. In the early 17th century hundreds of thousands of Japanese on Kyushu were at least nominal Roman Catholic Christians (Nagasaki was a Catholic city). The victorious Tokugawa Shogunate persecuted and suppressed Catholicism because of its perception as a “foreign” religion and made every Japanese family register with a Buddhist temple. Though the vast majority of Christians seem to have left the religion (many of these were only notional in any case), a small minority kept their religious identity as Catholics under a mask of crypto-Buddhism. Over the centuries they absorbed outward Buddhist motifs and passed on their Christianity orally. By recontact many of these “Christians” needed to be reoriented toward orthodoxy, so deviated had their religion become from its original character without institutional support. Note that though the surface layer of ritual and belief became distorted rather quickly, the basal psychological attachments with the ancestral faith along with the religious impulse still drove these believers forward to put their lives at risk (one can see this clearly among “Hidden Jews” as well).
Earlier, I have pointed to the fact that Russia seems to have gone through religious “awakening” in the last 15 years. This, despite 70 years of state supported atheism. Boris Yeltsin and Vladimir Putin were both baptized into the Orthodox Church & professed believers, a signal as to the direction of the wind. But, I will not reject the assertion that many of these “conversions” are superficial. A few years back I read a piece which pointed out that a disproportionate number of devout Christians during the Soviet period were of Jewish ethnic origin, a group already under suspicion during the later phases of the Communist state which looked toward Russian Orthodoxy as a source of solace. With the reconversion of much of the non-Jewish Russian elite after the fall of Communism many of these Jewish Christians were shocked to observe that those who had once persecuted them on account of their religious convictions were now attempting to marginalize them within the Russian Orthodox Church itself, presumably driven by anti-Semitic convictions. In Evolution for Everyone David S. Wilson holds out the hope that a non-theistic “religion” may serve some of the same group cohesive functional roles (the “horizontal” aspect) without any nod to a supernatural element (the “vertical” dimension). To some extent I think the reassertion of religious identification in places like Russia and Serbia fits this mold in that many people who affiliate with the Orthodox religion are likely only minimally interested in, or believers in, the supernatural. Slobodan Milosevic never disavowed his atheism, but during the late 1980s he built up his power within what was then Yugoslavia by aligning himself with the Eastern Orthodox religion, even attending ceremonies presided over by clerics. Of course, what one generation might do out of expedience another might accept with sincerity. The conversion of the pagan aristocracy of Rome to Christianity in the early 5th century was a forgone conclusion, their own religious traditions to which they had stubbornly clung to in the face of a century of Christian Roman Emperors was simply no longer a viable option in a polity which now proscribed their rituals and persecuted their beliefs. But by the 6th century no doubt the descendants of once proudly pagan families were now sincere and devout Christians (as attested by their patronage of the Church).
The point here is that religious systems and beliefs are embedded within functionally relevant institutional structures. Even if the former are altered or eliminated, the latter are often needful. Observe the cults of personality, mass rallies and cultivation of youth within the Party structure within Communist states which ostensibly have banished religious feeling. Similarly, even with the collapse of the latter as scaffolding the basal religious impulse will seek outlet in the psychology of a great many human beings. The synergy of both have often been powerful and historically significant forces, as attested by the relationship between Christianity and the rise of monarchy in northern Europe or the spread of Islam during the 7th century.