The state power will belong to proletarians in all leading countries of the world

Karl Marx : Philosopher, Economist
The theory of permanent revolution: "While the democratic petty bourgeois want to bring the revolution to an end as quickly as possible, achieving at most the aims already mentioned, it is our interest and our task to make the revolution permanent until all the more or less propertied classes have been driven from their ruling positions, until the proletariat has conquered state power and until the association of the proletarians has progressed sufficiently far – not only in one country but in all the leading countries of the world – that competition between the proletarians of these countries ceases and at least the decisive forces of production are concentrated in the hands of the workers."
Looking back at the 20th century, it seems fair to conclude that state power belonged to proletarians in only few countries. Furthermore, in most countries with proletarians in power the system failed sooner or later.

Address of the Central Committee to the Communist League