The twentieth century cannot be properly understood unless we understand communism: its origins, growth, demise and legacy. This brief overview of the history of communism challenges us to think about its role in shaping the contemporary world. This book shows how the modern communist movement emerged out of radical millenarian movements of the Middle Ages and the English Civil War, becoming a mass movement of industrial society, seeking to overturn capitalism and replace it with a society of equality, justice, harmony and co-operation. It traces the growth of modern communism from its beginnings in the early nineteenth century to its position of global power at the end of the Second World War. Why did communism grow so quickly? Why did it spread to turn almost half of the world red by the mid-1970s? What impact did it have upon capitalism and capitalist society?