The quote "A chain is only as strong as its weakest link" is attributed to V. I. Lenin who was discussing his reasons why the Bolsheviks were agitating the Russian Proletariat before the Revolution of 1917 (in "What Is To Be Done?" I think).

Traditional Marxist thought held that places like Britain and Germany would be most likely to undergo a Socialist Revolution because the working classes in those countries were larger, better educated and more politically aware.

Lenin argued that although Russia till had an agrarian/peasant based economy and its working class was small and centred around the cities, because its government (the autocracy of Nicholas II) was so much weaker than that of the other capitalist countries, a well motivated vanguard could create a revolution more quickly than anywhere else.

It is this principle that forms the basis of Bolshevism.