The defeat of several proletarian revolutions in countries like Germany and Hungary ended Bolsheviks' hopes for an imminent world revolution and began promotion of socialism in one country by Stalin. In the first edition of the book Osnovy Leninizma (Foundations of Leninism, 1924), Stalin was still a follower of Vladimir Lenin's idea that revolution in one country is insufficient. Lenin died in January 1924 and by the end of that year in the second edition of the book Stalin's position started to turn around as he claimed the "proletariat can and must build the socialist society in one country". In April 1925, Nikolai Bukharin elaborated the issue in his brochure Can We Build Socialism in One Country in the Absence of the Victory of the West-European Proletariat?. The Soviet Union adopted socialism in one country as state policy after Stalin's January 1926 article On the Issues of Leninism. 1925–1926 signaled a shift in the immediate activity of the Comintern (the Communist International) from world revolution towards a defense of the Soviet state. This period was known up to 1928 as the "Second Period", mirroring the shift in the Soviet Union from war communism to the New Economic Policy. In his 1915 article "On the Slogan for a United States of Europe", Lenin had written:
Uneven economic and political development is an absolute law of capitalism. Hence, the victory of socialism is possible first in several or even in one capitalist country alone. After expropriating the capitalists and organising their own socialist production, the victorious proletariat of that country will arise against the rest of the world.
In 1918, Lenin wrote:
I know that there are, of course, sages who think they are very clever and even call themselves Socialists, who assert that power should not have been seized until the revolution had broken out in all countries. They do not suspect that by speaking in this way they are deserting the revolution and going over to the side of the bourgeoisie. To wait until the toiling classes bring about a revolution on an international scale means that everybody should stand stock-still in expectation. That is nonsense.
After Lenin's death, Stalin used these quotes and others to argue that Lenin shared his view of socialism in one country. Grigory Zinoviev and Leon Trotsky vigorously criticized the theory of socialism in one country. In particular, Trotskyists often claimed and still claim that socialism in one country opposes both the basic tenets of Marxism and Lenin's particular beliefs that the final success of socialism in one country depends upon the revolution's degree of success in proletarian revolutions in the more advanced countries of Western Europe. At the Seventh Congress in March 1918, Lenin explained: