The Cotton Gin because cotton was being made at a faster pace, and the need for more cotton arose, which also called for the need for more slaves.
The Nuclear Test Ban Treaty made it illegal to test nuclear weapons in outer space, underwater, or pretty much anywhere else.
Northern European art focused on more realistic styles of painting.
The Incas, Mayans, and the Aztecs.
Answer:
Socialism was a new promise from the hell they had endured. Specifically in Russia, as the Bolshevik party began to gain popularity, many working class factory workers sided with Lenin's ideals as it granted "Peace, bread, and land".