Many people have written their own ideas about communism. Vladimir Lenin of Russia thought that there had to be a group of hard-working revolutionaries (called a vanguard) to lead a socialist revolution worldwide and create a communist society everywhere. Leon Trotsky, also from Russia, argued that socialism had to be international, and it was not important to make it happen first in Russia. He also did not like Joseph Stalin, who became the leader of the USSR after Lenin's death in 1924. Trotsky was made to leave the Soviet Union by Stalin in 1928, and then killed in 1940. This scared many people, and lots of communists argued about whether this was right and whose ideas should be followed.