CAUSATION

Both came from southern province, had reputation of personal bravery. Stalin wore uniform long before WWII, though never served in any army

Ex-KGB officer Viktor Suvorov developed a theory that Stalin was planning to attack Hitler, yet Hitler attacked first and that sudden move gave him such an advantage that Russian army kept loosing until Germans approached Moscow, Leningrad, Caucas and Volga. His main arguments do make sense which made his books quite popular in Russia:

• Stalin had largest and best equipped army in Europe that exceed armies of GB, France and Germany combined
• Stalin did attack Finland and Poland
• Stalin had troops mobilized

The really interesting part about this theory is not who started the war (WWII was inevitable, every government in Europe knew it as of the end of WWI) but why Russians kept loosing so badly. In Russian historiography this is a hot multi-decade debate. The mainstream version in USSR was that Stalin and army were unprepared for the war, Soviet weapons were outdated, Stalin trusted Hitler too much. Post-Stalin leadership blamed Stalin's purges. Modern historians tend to blame everything on ineffective socialism, population frustrated with bolshevicks, etc.

Suvorov did the simplest thing possible: checked archives and books published by official mainstream Soviet historians for the actual numbers and models of tanks, airplanes, troop counts, etc. Later his findings were confirmed by Mark Solonin, an engineer, prominent historian, writer and vlogger. Stalin did have the largest army in Europe. He was, as a matter of fact, OVER-prepared for the war. General analysis of Soviet mass-culture and propaganda of late 1930-s makes it obvious that population was conditioned for the ultimate global anti-capitalist fight. So Solonin blamed the incompetent Soviet generals. Almost there, yet:

• multi-million armies can't attack unexpectedly, it's technically impossible
• "badly organized" and "poorly maintained" Soviet army was on par with every other army in the world in that regard, these complaint are as standard as I have nothing to wear and you think I'm fat
• Soviet army did accomplish goals in Poland (1939) and Finland (1940)
• however bad/unexpected the first, second, third Hitler's strikes were, there was still more than enough tech and people to stop and even crush him not far from Soviet borders
• however incompetent/demoralized Soviet command/army was, it didn't matter - enemy was attacking on all fronts with less forces and machinery, no strategic genious or extreme bravery necessary

孙子兵法 = Sun Tzu = The Art of War

Instead of good old "A causes B", e.g. as a result of revolutionary chaos, a young ambitious officer Napoleon, genius of politics, economy, administration, tactics and strategy, arose to power and conquered Europe let's try think backwards. For some mysterious reason in politics and modern documented History the "B was a reason for A to happen" works much better: in order to conquer Europe, to draft largest army in the world, to excite masses of indifferent slaves subjects of the King with an unheard idea of patriotism and national unity, a French revolution was organized. This is called retrospective analysis and conspiracy theory. Yet revolution sure was a result of conspiracy, so - why not?

France in 1700+ had the largest, most modernized army in Europe, best artillery, logistics, military industrial complex, navy. Revolution provided endless supply of patriots. You can't loose with cards like that. Napoleon was just a very "politically correct" figure, universally appealing to provincial people, ex-nobles, middle class, etc. Stalin was all that plus not a Jew, unlike Trotsky and many other bolshevicks. That helped because anti-semitism was all over Europe in those days.

German high command was no dumber than I am. They realised what Russians did in 1917 and what was coming. Germany and USSR collaborated a lot in many areas, including military, up to 1930-s. They infiltrated Soviet command long before WWII. Stalin knew it and many generals and high-rank officials were arrested, jailed, executed before the war. Yet enough German agents survived: Red Army in 1941 was sabotaged on all levels. Stalin's purge continued during the war up to 1942 and, miraculously, Red Army command became competent enough.