Specifically I’m interested in how and why they happened. I know the second one is a partially unanswerable question, but there have to be reasons other than “Stalin wanted to consolidate power” because the very fact that he was able to have so many of his own close associates arrested and executed shows that he already had effectively absolute power. And of course Stalin was never officially a dictator like Mussolini or Hitler or Kim Jong-Il; he had to at least theoretically have the consent of his fellow leaders to take any action. It also seems clear to me from what I have read (general histories of the party and most recently Mawdsley and White’s The Soviet Elite from Lenin to Gorbachev (which, by the way, comes recommended by me if you’re interested in the topic. It’s dry as hell and lacks the novelesque narrativity that makes certain historians so readable, but if you can get past that I found that it did a lot to dispel myths about the Soviets (which to be clear doesn’t mean it portrayed them in a good light).).) that, at least until the mid 1940s, collective rule wasn’t wholly illusory and Stalin had to achieve some level of consensus among the elite before any major decision. Knowing that, it seems absurd to me that a majority of the Central Committee after around 1937 or so wouldn’t have realized they were almost certainly next on the list to be purged and turned against Stalin instead in a sort of Thermidorian Reaction.