If Stalin was surprised when Hitler broke the Pact, imagine Obama's reaction to Iran (God forbid):-
Stalin ordered many friendly gestures toward Germany, including speeding up the deliveries of Soviet products there. He did not in the least react to a warning from Churchill about a prospective German attack against the Soviet Union. During the ten days before the Nazi invasion—all kinds of information about the German threat notwithstanding—Stalin did his best or, rather, his worst, to affirm his faith in Hitler and in Germany. I do not know of a single instance of such abject behavior (for that is what it was) by a statesman of a great power.
The German attack shocked Stalin into silence at first. (Molotov’s words after the German declaration of war were also telling: “Did we deserve this?”) Stalin’s first orders for the Soviet army were not to respond at all. It took him hours after the invasion—until noon—before he ordered the army to resist.
There is still a controversy about how shaken he was during the first days of the Nazi onslaught. Eventually he pulled himself together. On July 3, 1941—eleven days after the German invasion—he addressed the peoples of the Soviet Union as a patriot. By that time some Nazi troops were more than one hundred miles inside the western Soviet Union and advancing toward Moscow.