During World War 1, Russia was lead by Tsar Nicholas the 2nd. However, the king was unpopular because he didn't help the poor and wouldn't take Russia out of the war, despite the fact they were losing.
Nicholas, we must back out! We are losing this war.
Due to this unfair treatment, a group known as the Bolsheviks take over the country in what is known as the "October Revolution" (it was really in November).
Please don't kill me!
We're not killing you. We're just taking over the country, that's all.
A civil war later breaks out between the Communists and the Counterrevolutionaries. Spoiler alert: the Communists won the war.
In 1924, Vladimir Lenin, leader of the Bolsheviks, died mysteriously of a stroke, and Joseph Stalin took over leadership of the country.
MR.LENIN! Are you okay?
Does this mean I'm in charge now?
Stalin started the Soviet Union, and led through brutality and fear. Anyone who opposed him was sent to the Gulag, a labor camp where they would work for the rest of their lives.