The history of communism encompasses a wide variety of ideologies and political movements sharing the core principles of common ownership of wealth, economic enterprise, and property. Most modern forms of communism are grounded at least nominally in Marxism, a theory and method conceived by Karl Marx and Friedrich Engels during the 19th century. Marxism subsequently gained a widespread following across much of Europe, and throughout the late 1800s its militant supporters were instrumental in a number of unsuccessful revolutions on that continent. During the same era, there was also a proliferation of communist parties which rejected armed revolution, but embraced the Marxist ideal of collective property and a classless society.
Although Marxist theory suggested that industrial societies were the most suitable places for social revolution (either through peaceful transition or by force of arms), communism was mostly successful in underdeveloped countries with endemic poverty such as the Republic of China. In 1917, the Bolshevik Party seized power during the Russian Revolution and in 1922 created the Soviet Union, the world's first self-declared socialist state. The Bolsheviks thoroughly embraced the concept of proletarian internationalism and world revolution, seeing their struggle as an international rather than a purely regional cause. This was to have a phenomenal impact on the spread of communism during the 20th century as the Soviet Union installed new Marxist–Leninist governments in Central and Eastern Europe following World War II and indirectly backed the ascension of others in the Americas, Asia and Africa. Pivotal to this policy was the Communist International, also known as the Comintern, formed with the perspective of aiding and assisting communist parties around the world and fostering revolution. This was one major cause of tensions during the Cold War as the United States and its military allies equated the global spread of communism with Soviet expansionism by proxy.
