Stalin did not trust anyone and was a man who purged anyone he saw as a threat. This includes: Intellectuals, party members, military leaders, and immigrants and/or just the average person. I hope this helps!
The Great Purge was the name given to the series of campaigns of repression and political persecution carried out in the Soviet Union in the late 1930s. Hundreds of thousands of members of the Soviet Communist Party, socialists, anarchists and opponents were persecuted or watched by the police; In addition, public trials were held, hundreds of thousands were sent to Gulag concentration camps and others were executed.
He was originally trying to find a area somewhere on the coast of the United States to try and find gold deposits and return wealth to the royalty of Portugal.
