Pearl Harbour: Why was it a surprise?

"Why, given the intelligence of Japanese naval movements available to the Americans, did the attack on Pearl Harbor on Sunday December 7, 1941, come as an apparent surprise?" Over sixty years after the attack on Pearl Harbor, it is frustrating to see just how avoidable the devastation was. "Never before have we had so complete an intelligence picture of the enemy. And perhaps never again will we have such a magnificent collection of sources at our disposal" …

…Queen's Quarterly v99 n1 Spring 1992 p20-32 Prange, Gordon, & Goldstein, Donald & Dillon, Katherine. (1986), Mental attitude in "Pearl Harbor: the verdict of history", McGraw-Hill Book Co., p516-531, 637-639 notes Wohlstetter, Roberta. (1962), Surprise in "Pearl Harbor: warning and decision", Stanford University Press, p382-396 Feis, Herbert. (1956), "War came at Pearl Harbor: suspicions considered", Yale Review v45 n3 1956 p378-390 Kahn, David, , "The Intelligence Failure of Pearl Harbor" Foreign Affairs, Winter 1991 v70 n5