Stalin famously said at the First All-Union Conference of Soviet Industrial Workers on February 4th, 1931: "We are lagging behind leading nations by 50-100 years. We need to catch up in ten years. Either we do this or we get crushed." Almost exactly a decade later, WWII began for the USSR.

However, the idea that the USSR will be once again invaded by "bourgeois" nations was nothing new by 1931. Soviet society was built from the very beginning with the idea that capitalist nations won't stand to see a socialist state rise, and will attempt to crush it by influencing minor states like Finland, Romania, Poland, etc. This was reflected in military matters as well. For example, the 1935 Red Army infantry field manual has identification markings for the following nations' aircraft: Japan, Poland, Romania, Latvia, Estonia, Finland. This is a pretty good clue that while the USSR was preparing for war, nobody was aware of the scale the conflict was going to take as far back as when Stalin came to power and even for several years afterwards.