What was the nature of the surprise in December 1941 that accounted for the Japanese success in both crippling the American pacific fleet in Pearl Harbor and destroying America's only wing of bombers at Clark Air Force Base in the Philippines?


The surprise was technological. The attack on Pearl Harbor took place on the morning of December 7th 1941; the attack on Clark Air Base in the Philippines occurred hours later. The real surprise was not the intentions of the Japanese military, or even the proximate time, it was the ability of Japanese pilots and ordinance to successfully execute the attacks,

By December 2, 1941, the US had ample warning from its code-breaking operations (including MAGIC), its traffic analysis of Japanese radio communications and other observable activities (such as embassy activities and military radio silence) to conclude that Japan was preparing for war in the Pacific. US Naval intelligence, for example, had interpreted the ominous change in Japanese call signals for all its ships on December 1— and efforts to obscure the whereabouts of its aircraft carriers from US surveillance— as ominous war signals. So the proximate time of attack was not a total surprise. Neither was the likely targets. There was a shortlist of four targets: the two most likely being Pearl Harbor, where the US Pacific fleet was stationed, and Clark Air Force Base, where virtually all of the US bombers were stationed.

What was unexpected was Japanese capabilities. In the case of Pearl Harbor, US military intelligence had assessed, based on observation of Japanese air shows, that Japan did not have the capacity to launch torpedoes from airplanes in shallow water. Torpedoes in 1941 were usually deployed in deep water, so their motors could start to propel to the surface before they hit the ocean floor. If Japanese pilots did not have the technology and skill to launch torpedoes in shallow water, the safest place for the US battleships would be in the shallow waters of Pearl Harbor. If Japan tried to dive bomb the ships in Pearl Harbor, naval anti-aircraft gunners could them down as they circle directly overhead. So, marshaled in the presumably safe harbor, the fleet was kept on an alert 1 status (the lowest of three alerts). What was unexpected was that Japanese pilots had been secretly trained to skim their torpedoes in shallow water, and that surprise left the fleet, no matter what its level of alert, vulnerable to being sunk from afar by carrier-launched planes. So all of America's battle ships were sunk or severely damaged.

At Clark Air Force base, there could be no possible surprise about Japan's intention. Japan had already attacked the US, nine hours earlier. The US command assumed, however, its bombers were safe because, with the Japanese carriers now known to be in Hawaii, the nearest available Japanese bombers, based in Taiwan, could not reach the Philippines without mid air refueling. And US intelligence had assessed that these land-based bombers could not by refueled in mid-air by Japanese pilots. So the U.S. left its only wing of bombers parked, wing to wing, in the open. What was unexpected was that Japan, like the US, had perfected mid-air fueling techniques. In both cases, the US were surprised, not by the intentions of the Japan, but by its technology.

Collateral Question: Why was there a technological surprise?


Two variations of Deception.

The picture that emerged by 1941 in Washington of a primitive Japanese air force that lacked both the technology and pilot training for refueling in mid-air, launching torpedoes in shallow water, conducting long-range missions proceeded both from self-deception and other-directed deception. The former grew out of the stereotyped of Asian incompetence. The latter, out of a deliberate Japanese program to project weakness prior to the attacks.

The Japanese-directed deception used British and American military attaches to reinforce the picture of weakness. While concealing its modern Zero fighter, Japan displayed its antiquated and obsolescent planes at air shows. When western attaches were invited at Japanese air bases, exhibitions of flying incompetence were purposefully staged for them. As one of Japan's leading strategists later explained "Foreign observers saw only what we allowed them to see". And western attaches (and other spies) were mis-briefed by Japanese air ministry officials on the difficulties of training Japanese pilots to fly solo. The resulting assessment of incompetence closely fitted in with and reinforced the preconceptions that most foreign attaches had about the Japanese. Through this disinformation, and reinforcement of stereotypes, Japan caught the United States totally unprepared for its aerial attack on presumably safe harbors and out-of-range airfields.

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