Why did Stalin allow the USSR to be taken by surprise in June 1941?

Answer 1

Stalin and Hitler (via Von Ribbentrop) had signed a non-aggression pact which guaranteed that each would be safe from the other and that parts of eastern Europe would be split between them at a later time. Hitler had always planned to invade the USSR, as indicated in Mein Kampf, as Hitler wanted the USSR's resources and space for the use of the Third Reich. He believed the Slavic people to be sub-human and politically, Bolshevism was diametrically opposed to National Socialism, although the objectives were nearly identical. All indications were that Hitler was about to launch Operation Barbarossa and invade the USSR, but Stalin refused to believe his advisors and intelligence gatherers and trusted to the previously signed non-aggression pact. Even as Hitler's armies came pouring over the Soviet borders on six fronts from the Arctic Ocean to the Black Sea, Stalin steadfastly refused to act until it became blatantly obvious and he could no longer ignore the obvious.