Explanation: The paranoid Soviet dictator Stalin rejected multiple reports from his own intelligence sources that Nazi Germany was going to invade the USSR imminently. Stalin, being paranoid in the wrong direction, believed it was a ploy to make him strike against the Nazis early, helping Britain at the expense of the USSR (as Britain was fighting Nazi military pressure alone at the time, and could have used an ally to take the heat off, so to speak)

The Nazis invaded the USSR shortly afterwards, and Stalin was so shocked that he spent a week in isolation at his country home without any contact with the Soviet apparatus that was desperately falling apart at a surprise attack they should have been warned about.