I want to add for historical explanation that the backwardness of Tsarist Russia being a hindrance to War was the prime driver of the February revolution of 1917. French and English capitalism forced capitalist revolution down the Russian bourgeoisie's throat. But the Russian bourgeoisie was too terrified of the masses to carry through with it, to institute the necessary anti-feudal economic measures, and so the proletariat completed the capitalist revolution for it.
This is the real content of October. It was not an attempt to establish communism on Russian soil. The Bolsheviks wanted to spread revolution abroad and complete the capitalist revolution at home to remove as many barriers to communist construction later on. They anticipated losing power as far back as 1905. And well that's exactly what happened in 1926. Then they were all killed during the Great Purges.
Class war like any war is a war of deception, so the Stalinists lied about being communists to exploit the trust the unaware proletariat and the peasantry had put in the CPSU. They then forced rapid industrialization (anticommunist in nature) onto the proletariat through a brutal regime of terror and Stakhanovism.
And finally they, more so than the Nazis, were the ones responsible for unleashing the second world war in 1939, by forming a pact with them. Without that pact, Hitler would have been doomed to failure from the start due to economic reasons. Specifically, Hitler would have lost the arms race with the Allies. Anyway Stalin's entire intent (he anticipated the Nazis would lose) was to destabilize Europe so he could swoop in and annex large swathes of it to construct border states. The Iron Curtain. And his prediction was correct.
During the second world war, the Comintern parties, all rallied behind the Russian one, became organs of collaboration with the world bourgeoisie to prevent or withhold proletarian revolutions by deceiving the masses until the final moment.
And so in Italy, in 1945, when the peasants began to seize the plantations and depose the landlords, the PCI ordered them to drop their guns in the name of democracy, unity and national reconstruction (which of course under capitalism means exploiting the proletariat).
The USSR in fact never achieved a socialist economy. Socialism means the abolition of buying and selling, and they had plenty of that, an ever increasing amount of it actually. It was politically a socialist state until 1926 when every state policy was turned upside down in the name of "socialism in one country" � a deceptive name for the policy. Between 1926 and 1936 the USSR converted itself into a one-party bourgeois-democratic republic based on universal suffrage instead of... excluding all other classes from political representation other than the proletariat and poor peasants.
Marxists don't deny the possibility of achieving socialism in a single country insofar as 1. it sets itself the goal of revolutionary war, 2. its economy is already fully industrialized.
The USSR was not fully industrialized. Its agriculture was insanely backwards. The collective farms weren't socialist. They were closer to medieval peasant cooperatives. We should add that forced collectivization of agriculture was against the Comintern platform of 1919. It was a break in policy.
Capitalism through the course of its development tends to do away with the individual members of the bourgeois via nationalization and share capital. It tends to depersonalize capital. It does not matter that in the USSR no bourgeois individuals existed; it was a capitalist state.
Government bureaucrats while they were salaried employees, waged workers, had plenty of stakes in government bonds, yielding interest rates of 2%, and of course depending upon state industry, which turned a profit. Does that not sound like a stock dividend to you?
Under Lenin there was no rapid industrialization. It is because of this that the Bolsheviks lost power actually. They had become a barrier to the development of industry because at that time only capitalism could develop it and the proletariats's interests are opposed to that.
From first being a facilitator of economic development, a destroyer of all the feudal fetters upon industrialization, the Bolsheviks became a burden, and the world bourgeoisie, with its numerous agents in the state machinery (which was largely inherited from the Absolutist State, in other words a bourgeois state machinery, since the productive forces were not developed enough for a proletarian state machinery), used this to its advantage.
It was able to use the scissors crisis and the ideological immaturity of the party to open up a rift between the right and left oppositions and crush them. It quite literally gutted the party like a fish and then wore it like a skin suit.