Overwhelmingly the work of professed Christians? Like Hitler? You're being sarcastic, right?
I didn't say the Nazis complied with Christian doctrine, which of course they did not. What conquerer does? But Hitler is recorded to have said "I am a Catholic, and I will be one until I die", or words to that effect. Hitler's decrees explicitly declared that Nazi Germany was a Christian state. If he was insincere in this, why do it, unless it was because he knew Germany was not ready to break openly with Christianity?