Wednesday, December 07, 2005

ELINT, Information Operations Helped Japanese Forces Achieve Surprise at Pearl Harbor

On December 7, 1941, air and naval forces of the Empire of Japan struck the US Navy base at Pearl Harbor, Hawaii, and surrounding Army and Navy facilities. Twenty-one ships of the Pacific Fleet were sunk or damaged in the attack, including two battleships sunk and six heavily damaged. Nearly 200 US aircraft were destroyed and over 150 damaged, most while still on the ground. Total US casualties amounted to 2,403 dead (68 of which were civilians killed by improperly fuzed anti-aircraft shells) and 1,178 wounded. Nearly 1,800 sailors perished on the battleship USS Arizona alone. Japanese losses amounted to 29 aircraft shot down and five midget submarines sunk or beached: 64 men in all.

The raid commenced when the Japanese cruisers Chikuma and Tone each launched a floatplane about 220 miles north of Oahu at 0530 local time to ascertain the exact anchorage of the US fleet. Twenty minutes later, the carriers of Japan's First Air Fleet, Akagi, Kaga, Hiru, Soryu, Zuikaku, and Shokaku turned into the wind to begin launching approximately 350 fighters and bombers in two waves. The aircraft included Nakajima Type 97 "Kate" level bombers, some armed with torpedoes and others with bombs; Aichi Type 99 "Val" dive bombers; and Mitsubishi Type 0 "Zero" fighters. Cmdr Mitsuo Fuchida, leading the first wave, used a Honolulu radio station broadcasting Hawaiian music to home in on the target. At 0735 the scout plane from Chikuma broke radio silence that had been maintained since the force left Japan twelve days earlier with a report that the US fleet was at its Ford Island anchorage. Fuchida sighted the ships at 0740 and saw that they were sleeping peacefully. As his attack wave divided into smaller units to deliver its ordnance, Fuchida radioed the code words signaling complete surprise had been achieved: "Tora! Tora! Tora!" ("Tiger! Tiger! Tiger!").

Radio Silence
While credit for the success of the Japanese attack must go to the audacity and attention to detail of its planners -- particularly its chief architect, Admiral Isoroku Yamamoto, Commander in Chief of Japan's Combined Fleet -- the maintenance of strict radio silence for the entire outbound voyage played a crucial role in the results it achieved.

In the previous July, a Japanese carrier task force consisting of Soryu and Hiryu and their escorts accompanied the convoy of troop transports carrying Army forces to seize French Indochina. During its 2,000-mile voyage from Japan down the coast of China, the task force intercepted British radio reports from Hong Kong to London that pinpointed the location of the Japanese ships, and even identified specific types. The Japanese communications and intelligence officer understood that the British were plotting the fleet's movements using radio direction-finding equipment. This generated an official requirement that future task forces would maintain radio silence during an operation -- even to the extent of sealing transmitter keys -- and that efforts would be made by other units to send false messages to mislead whomever might be eavesdropping.

For the Japanese, the importance of radio silence surpassed even the benefits of aerial reconnaissance. The presence of six fleet carriers and several other vessels that carried floatplanes with the First Air Fleet would enable a system of air patrols to thoroughly cover huge swaths of ocean for ships and planes that might detect it. On the other hand, such a system of patrols increased the chances that a radio message would be sent in a hasty or unguarded moment, or if a pilot had an emergency. For the raid on Pearl Harbor, no air patrols were flown until the morning of the attack for just this reason.

Nevertheless, the interest in Japanese radio communications shown by US intelligence personnel both raised flags and caused strategists to second-guess themselves. The Japanese strike at Pearl Harbor was one of more than two dozen landings, raids, and related operations scheduled to coincide over a two-day period. As of December 1, the US was aware of a great "movement to the south" that presaged Japanese attacks on the Philippines, British possessions, and the Dutch East Indies. In fact, deployments southward of Japanese troop transports, supply freighters, destroyers, cruisers, and even battleships were indicated by radio traffic and this seemed to support preconceived notions among US planners that the inevitable blow would be struck in Southeast Asia, not the Central Pacific, let alone both.

There was some alarm at this point that no radio traffic had been identified from the Japanese fleet carriers for many days. Furthermore, the Japanese had just changed their radio call signs for the second time in a six-month period, which was unprecedented. Even more disturbing to some was the overall precipitous drop in the volume of Japanese radio traffic. However, US intelligence officers were "confident" that the carriers were in the home waters of Japan and not "rounding Diamond Head" as Admiral Husband E. Kimmel, Commander in Chief of the US Fleet, half-jokingly speculated. Such confidence on the part of seasoned intelligence officers was born of disbelief that the Japanese could mount a carrier attack on Pearl Harbor. If the Japanese carriers were not heading south, then they must be in their home waters, or so went conventional wisdom.

Upon recovering his aircraft Vice Admiral Chuichi Nagumo again clamped strict radio silence over the First Air Fleet. The US carriers Enterprise and Lexington were at sea somewhere nearby, and the last thing he wanted was an unexpected encounter. Nagumo did order air patrols to cover his withdrawal from Hawaiian waters, prepared to strike the enemy if he encountered him. Fortunately for the US flattops, perhaps, the First Air Fleet retired without such an encounter.

Raid Spurs EW Developments
The first moves to form an organization in the US devoted solely to the development of radio countermeasures came from the Navy on December 11, 1941, just four days after the Japanese attack on Pearl Harbor. On that day, Admiral Julius Furer, one of the coordinators of naval research and development, convened a preliminary meeting to discuss setting up such an organization. Following this, a letter was sent to the National Defense Research Committee (NDRC), requesting that it consider forming an organization to develop countermeasures equipment. The recommendation was accepted.
--From The History of US Electronic Warfare, Volume 1 by Alfred Price (AOC, 1984), pg. 19

Further Reading
For more information on the Pearl Harbor raid, consider the following books and websites:

The History of US Electronic Warfare, Volume 1 by Alfred Price (AOC, 1984)
At Dawn We Slept, The Untold Story of Pearl Harbor by Gordon W. Prange (Penguin Books, 1982)
"Modern History Sourcebook: Pearl Harbor Attack Documents, 1941"
"Pearl Harbor Operations: General Outline of Orders and Plans"

See the Nagasaki post for information on the raid that ended the Pacific War.

UPDATE: Roundups of posts on the Pearl Harbor attack can be found at the following sites:

La Shawn Barber's Corner

Winds of Change

Michelle Malkin


At 6:11 AM, Blogger Alex said...

Any chance of digging into the "was the radar warning disregarded?" story?

And I'll link you if you mention the Taranto Raid!

At 9:29 AM, Blogger Michael Puttre said...

I've always been sceptical of the "radar warning disregarded" story. It is a good dramatic element, and it shifts blame away from the people responsible for the defense of Pearl Harbor. For some reason, we like to look for little loose threads to pull. The fact is, there was no comprehensive system of air patrols at Pearl Harbor, there were no extended pickets out beyond the harbor approaches, and radar was not yet an integral part of the base defense. The radar crew was conducting an exercise on the morning of December 7 and there was was no procedure in place for acting on information received from the radar station.

The Japanese success at Pearl Harbor, for all its conceptual audacity and operational brilliance, was as much a result of a failure of imagination among US planners at the highest levels. We just didn't think they could pull something like that off.

As for Taranto, that raid placed the bug in many minds that ships at anchor were vulnerable to air attack by torpedo planes, and a lot of US planners considered the problem. However, Taranto was a blow "in the clinch" between two air and naval forces operating in the relatively restricted waters of the Mediterranean basin. British and Italian bases were in air range of one another. While key US planners took the lesson that ships at anchor vere at risk, the raid was not an object lesson in the ability of the Japanese to conduct carrier operations so far from their home waters without the support of regional bases.

Failure of imagination remains a huge problem, and, perhaps, it will always be with us.

At 7:52 PM, Blogger Robert Sulentic said...

I think, Mike, you hit the nail on the head with the 'failure of imaginination' thing (or possibly, underestimating your opponent). Most things I've read recently seem to think that the US govt. knew it was going to be fighting the Japanese sooner or later, and the 'conventional wisdom' combined with a fair amount of contempt for the Japanese ended up producing the outcome of Dec 7. (That still doesn't completely explain the planes getting caught on the ground in the Phillipines, but its probably close enough.)

Anyway, I find it curious that the Navy did fail so badly in anticpating the Japanese, in that both the Japanese and the Americans pioneered carrier tactics. Perhaps it was a case of the 'battleship' admirals still being in charge.

I'm not sure though that even if the Japanese attack had been detected in time to sortie the Battleships, that the outcome would have been substanially different. The fate of the Prince of Wales and the Repluse seems to indicate that those old battleships had limited utility. (I'm fairly sure that they all got lots more AA guns after they were raised), it raises the spectre that a 'Battle of Hawaii' may have been a greater defeat. Or it could have been a bloody draw. Or something else.

I think the penultimate lesson is that it still pays to put out patrols.

At 7:54 AM, Blogger Alex said...

Re: Radar...

What it also points up was that the success of British air-defence radar in the Battle of Britain wasn't a success of radar, but of the integrated command, control and communications structure Dowding built to use it.

Re: Taranto...

well, the FAA still make it the excuse for an epic annual boozeup..

At 10:05 PM, Blogger tactics said...

Recently read a fascinating book, "Pearl Harbor, Japan's Fatal Blunder" by Harry Allbright published in 1991. In it he posits that the Jap planners also lacked imagination in that they failed to provide contingency plans should the two U.S. carriers (the true principal targets of the attack, not the battleships and others) be absent from Pearl on 12/7. He claims they could have forced the carriers to seek battle against an enemy that was superior in quantity and in quality merely by occupying any of the many lightly defended Hawaiian Islands using minimum landing forces. He also credits the Jap admirals with gross timidity in failing to follow up with a third air strike targeting the fuel dump, the repair facilities, and the submarine docks. Had they done those two obvious things it could have paralyzed the U.S. fleet, possibly for years.

At 8:36 AM, Blogger Eric Blair said...

Isn't there a line somewhere about the side that wins wars is the side that makes the fewest mistakes?

At 10:14 AM, Blogger Michael Puttre said...

I think there's a lot to be said for the tactical shortcomings of Japan's execution of the Pearl Harbor raid, particularly about letting the fuel and repair facilities off the hook. However, Nagumo was apparently so surprised at his good fortune that he didn't want to press his luck. In mission planning, the Japanese prepared to lose a carrier or two and still call it a success. Nagumo wanted to bring the flattops (and pilots!) home to fight another day. A mistake, perhaps, but an uderstandable one. Nagumo was a long way from home.

Japan didn't have the resources to stage landings in Hawaii simultaneously with its amphibious operations in Southeast Asia, which were the main objectives of the effort. They thought about it, but decided against it. Interesting to think about what a landing and occupation of Hawaii would have meant to the war.

The main problem with Pearl Harbor is that it was a "win the battle, lose the war" affair: tactically brilliant but a strategic blunder. I've heard some analysts say that the Japanese should have let the US fleet sortie out in a "Plan Orange" defense of the Philippines and be defeated at sea, fair-and-square, as it almost certainly would have been. Then the US would not have had the "Remember December 7th!" rallying cry, and might have been more open to a negotiated solution. After all, Yamamoto warned that the thing needed to be wrapped up in six months. Because after that, Detroit kicks into gear. And he'd seen Detroit...

At 8:45 PM, Anonymous Anonymous said...

I think only five (5) jap carriers attacked Pearl Harbor!

At 8:40 AM, Blogger 123 123 said...

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