Sometime prior to or after Vladimir Lenin's death, have the Soviet state be "softened" by any means necessary.
Perquisites:
-Stalin cannot rise to power under any circumstances
-Trotsky cannot rise to power under any circumstances, either
-The Bolsheviks cannot stay allied with other parties, chiefly the Left SR Party
Reforming the Soviet state is okay, but Lenin cannot live longer to see his reforms take place.
Major figures in the Russian Revolution, save Lenin, can be killed off. Stalin, Trotsky, etc. are fair game.
Mainly, what I'm looking for is a less authoritarian Bolshevik Party-led regime set up in Russia post-civil war.
Try to make the Soviet state as "free" as possible, specifically as to prevent the rise of Stalin or any Stalin-like figure to power.
Have fun, comrades!
