People understood that war could break out with little or no warning, too—the leading nations on both sides of the Cold War had entered the Second World War as a result of being on the receiving end of devastating surprise attacks: Operation Barbarossa, the massive German surprise invasion of the Soviet Union in June 1941 (in violation of the German-Soviet Nonaggression Pact of 1939); and Pearl Harbor, the Japanese surprise bombing raid on the US territory of Hawaii in December of the same year.
