I'm told Homage to Catalonia by George Orwell is eye-opening and brilliant. Orwell went over there to fight in the Civil War to fight Franco's Nationalists as part of the Anarchist contingent, and watched the Soviet-controlled "Republicans" killing their own Anarchist allies rather than the Nationalist troops. The Republican force was just doing what Communists always do, which is to kill off your allies when you think you're going to win, so you can seize power without opposition.
Gosh, it's so sad the Communists wound up losing.
Dang it, you beat me to it.