Joseph Stalin died on this day in 1953. Born Ioseb Dzhugashvili in 1878 in Georgia, he was born into an abusive family that pushed him into a life of religious service. He ended up a dictator responsible for the deaths of millions. While studying to become a priest, he began secretly reading the work of left-wing revolutionary thinkers and became embedded in labor activism. From there he joined the Bolsheviks. In 1912, Lenin named him a member of the Central Committee of the Bolshevik Party. He took the name Stalin (based on the word "steel" in Russian) as a pseudonym.
After Tsar Nicholas II abdicated in 1917, he became a key part of the dictatorial takeover of revolutionary government and its subsequent evolution into the Soviet Union. He was promoted to dictator in the late 1920s and industrialized the then-rural country through force and collectivized farms (meaning forcing hundreds to work on government-owned plots of land taken from farmers), the latter of which caused a famine that killed around 5 million people.
After allying with Germany in 1939, the USSR joined the Nazis in an invasion of Poland. But in 1941, Adolf Hitler broke their treaty and directed his armies to march into the Soviet Union and overthrow it. After suffering over a million casualties, they successfully pushed the Nazis out of their territory, eventually working with the U.S. and allied European powers to encircle and defeat Nazi Germany.
The USSR then occupied a large part of Eastern Europe, dominating various states through literal or implicit force. His death was mourned by many who admired his strength as a leader while those opposed to his harsh rule, millions of whom were imprisoned as dissidents, hailed his death.
You can learn more about Stalin at this history article published by the BBC.