Seems unlikely, at least on a percentage basis - which would be the relevant one. Large scale atrocities by even nominal atheists are a fairly recent phenomenon, in general. Of course one can promote godlessness - of many kinds. But atheism is not a belief system, it is a property of a belief system - many quite different belief systems are atheistic. Not all. But it's a recurrent theme. The exceptions - such as the modern US - are worth studying. They don't usually say. I know they were raised in strongly, fundamentally, theistic homes for the most part. Looks to have been the same as others have had before them - mostly theists, if that makes any difference to you. The theistic Germans at the time killed a lot of people for belonging to the wrong theism. That has been a common justification, over the years - but whether it truly describes a motive or not, I suspend judgment. Quite a few believed in the superiority of a godless society, and Stalin was set apart from them as well. Apparently that isn't the discriminating factor. His desire to promote atheism ? He sure didn't like them atheist religions (except Communism) - seems odd he would have turned down the opportunity to spread the faith easily and quickly. Unles his desires didn't have much to do with atheism. Are you sure Stalin was atheistic, personally ?