We all know that Stalins policies have caused the death of a lot of people. He collectevised the farming lands again (undoing the NEP), boosted fast industrialisation (even though the industry lacked the production of consumption goods) and purified the top leadership and deported other dissidents to establish firm control over the USSR.
Now, in a recent discussion with a Georgian here on Reddit, the argument was made that these reforms were necessary for the military survival of the USSR. This seems unlikely to me, since the NEP increased agricultural production (lower food prices, more stable society, better economy), and the deportations must have caused social tensions.
So my question is to you is, how did the economic (and social) reforms of Stalin influence the military capabilites of the Soviet Union?
The huge development made Russia unrecognisable from the one before the revolution. The development under the 5 year plans was huge. Pig iron production rose from 0.4 million tonnes in 1922 to 3.5 million tonnes in 1926, and then boomed to 17.7 million tonnes in 1937. Although no other heavy industry was quite as huge growth as iron, electricity featured a 400% growth, coal 300%.
Let's look into this more, production 1918-1923 was very badly affected by the Russian civil war, this especially pulled the industrial workers (who were to become the proletariat, according to Marx, so the most supportive to the communists) into the war. The following policy, NEP caused industrial prices to fall, while agricultural prices to rise, causing the "scissors crisis". This is the period of relative prosperity you are talking about. The Five Year plans were embarked on (for many reasons) to cause huge growth. 80% of the investment was into heavy industry, in the first plan 1928-1932. Huge investment and the fear of being called a "wrecker" if your factory didn't produce the incredibly high targets, and the want to revenge the West after WWI, alongside the fact that a lot of people saw this as a huge chance to move up in the world, In 1913 over 80% of Russians still lived in the "Mir" traditional villages squalid conditions where food wasn't certain. The workers were actually looking forward to the new promised "workers paradise", this leads to the social change you allude to, but also makes productivity skyrocket. The growth also was based on other growth, heavy industry was to build the factories to build the goods for the people, electricity and coal saw huge growth because of this. Huge complexes were built in Magnitogorsk, from a small village to a city of ¼million in 5 years 1932-1937 and just focused on iron production, as well as other metallurgy.
For the huge increase in industrial output meant a colossal increase in military power. Not only did you now have the raw resources to build military equipment, but more importantly, possibly you had the infrastructure in place. The greatest tank is useless without a supply chain, and the train network and electricity devolved especially under the Second FYP allows greater mobility and supply of troops, which was absolutely critical in the winter of 1941.
The soviets built 93,000 aircraft and 79,000 tanks in the years 1939-1945, completely outstripping the Germans, it is popular opinion that pure numerical superiority in air and armour in the Eastern Front won the war. German armour is generally considered superior to Soviet, this is shown by a incredible average of 5 soviet tank losses to 1 German tank lost in 1941.
(Sorry for the poor quality answer, I haven't written one of these before if you are interested Alex Nove and Orlando Figes are great reads, I will also finish this off as it is midnight and I can no longer read my sources and this is causing my awful spelling/English sorry. I know I haven't answered the question yet, that will come)
If you are speaking solely of his Industrial policies, while imagining everything else happened the same way it did historically, then yes the increases in industrial output were necessary to the survival and recovery of the Red Army as an effective fighting force, the force which was most singularly responsible for breaking the Wehrmacht. If the officer corps was still headless but the army was only half the size with a smaller proportion of that force being well equipped, a total collapse in 1941 or 1942 seems plausible.
Taking everything that Stalin did into account, the picture is complex.
Pro
Con
It is very speculative to try and say "without Stalin's policies, the Germans would have won" or "The Germans would have been worse off if someone else is in charge of the USSR". I am not prepared to make such judgements, but I hope the above gives you something to look into.