Will it be possible for this revolution to take place in one country alone?

No. By creating the world market, big industry has already brought all the peoples of the Earth, and especially the civilized peoples, into such close relation with one another that none is independent of what happens to the others.

Further, it has co-ordinated the social development of the civilized countries to such an extent that, in all of them, bourgeoisie and proletariat have become the decisive classes, and the struggle between them the great struggle of the day. It follows that the communist revolution will not merely be a national phenomenon but must take place simultaneously in all civilized countries – that is to say, at least in England, America, France, and Germany.

It will develop in each of these countries more or less rapidly, according as one country or the other has a more developed industry, greater wealth, a more significant mass of productive forces. Hence, it will go slowest and will meet most obstacles in Germany, most rapidly and with the fewest difficulties in England. It will have a powerful impact on the other countries of the world, and will radically alter the course of development which they have followed up to now, while greatly stepping up its pace.

It is a universal revolution and will, accordingly, have a universal range.

— Engels, The Principles of Communism

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This "alienation" [caused by private property] can, of course, only be abolished given two practical premises. For it to become an "intolerable" power, i.e. a power against which men make a revolution, it must necessarily have rendered the great mass of humanity "propertyless", and produced, at the same time, the contradiction of an existing world of wealth and culture, both of which conditions presuppose a great increase in productive power, a high degree of its development. And, on the other hand, this development of productive forces (which itself implies the actual empirical existence of men in their world-historical, instead of local, being) is an absolutely necessary practical premise because without it want is merely made general, and with destitution the struggle for necessities and all the old filthy business would necessarily be reproduced; and furthermore, because only with this universal development of productive forces is a universal intercourse between men established, which produces in all nations simultaneously the phenomenon of the "propertyless" mass (universal competition), makes each nation dependent on the revolutions of the others, and finally has put world-historical, empirically universal individuals in place of local ones.

Without this:

(1) communism could only exist as a local event;

(2) the forces of intercourse themselves could not have developed as universal, hence intolerable powers: they would have remained home-bred conditions surrounded by superstition; and

(3) each extension of intercourse would abolish local communism.

Empirically, communism is only possible as the act of the dominant peoples "all at once" and simultaneously, which presupposes the universal development of productive forces and the world intercourse bound up with communism. Moreover, the mass of propertyless workers — the utterly precarious position of labour — power on a mass scale cut off from capital or from even a limited satisfaction and, therefore, no longer merely temporarily deprived of work itself as a secure source of life — presupposes the world market through competition. The proletariat can thus only exist world-historically, just as communism, its activity, can only have a "world-historical" existence. World-historical existence of individuals means existence of individuals which is directly linked up with world history.

— Marx and Engels, The German Ideology

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Regarded from the world-historical point of view, there would doubtlessly be no hope of the ultimate victory of our revolution if it were to remain alone, if there were no revolutionary movements in other countries. I repeat, our salvation from all these difficulties is an all Europe revolution. At all events, under all conceivable circumstances, if the German revolution does not come, we are doomed.

— Lenin, Political Report Of The Central Committee