Human history is replete with unanticipated catastrophic events that come like a bolt from the blue. During World War II, both Nazi Germany’s attack on the Soviet Union (Operation Barbarossa) and the Japanese attack on Pearl Harbor came as strategic surprises. Then as now, intelligence warnings were ignored.
Other shockers include the Egyptian and Syrian attack on Israel during the Jewish high holiday of Yom Kippur in 1973, and of course the 9/11 strike by Al Qaeda against the U.S. Again, intelligence reports prior to the events were ignored or did not reach the right leaders.