18 The Rise of Fascism and Nazism:

There were many summary executions that included women, the aged, and even the minor, numbering at the very least in the tens of thousands, usually by a bullet to the back of the head.

Hitler's Nazi Reich murdered millions of Jews because they were considered a dangerous race; Stalin's Soviet Union murdered millions of kulaks and other "bourgeois" elements because they were.

The mass murder associated with the Purge Trials drew in millions of all classes and ethnicities, including large numbers of those Jews who had earlier risen to prominent positions in party and state.

Mass murder in the Soviet Union lasted over a longer period in waves from 1919 to 1939 than it did in waves directed by the leaders of the Third Reich.

The Nazi camps were overrun by enemy armies at the end of the war and many of them exposed to the scrutiny of the world, whereas the camps in Soviet Russia have not been subjected to the scrutiny of scholars.

Most scholars agree that what started as an expression of Stalin's paranoia - or his possibly well-founded apprehension that moderates in the Party wanted to cut him down a peg - then spread into something else, a phenomenon that some have termed a "third revolution," or the third main stage Stalin's ultimate responsibility is beyond reasonable doubt, so it's hard to believe that he intended all of the things that developed after the Kirov assassination.

When elections are meaningless and entrenched bureaucrats come to exercise a domination, regular purges are necessary according to those who have perceived a peculiar dynamic in modern totalitarian states.
The country is stagnant without purges.
The purges have been attributed to the inherent evils of the Communist system of absolute power.

Even though they believed that violence could be justified, they had to ask themselves what would happen if violence got out of hand.

The price paid in World War I for defending what was perceived as national interests was staggering, but an even greater price was paid for the "achievement of socialism" through the devices of Communism in Soviet Russia.

During the interwar period, the admirers of Soviet Communism in Europe were also afraid.
The Italian and German varieties of that fear were particularly menacing, leading to yet another world war.