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Pearl Harbor: Intelligence Failure

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* Throughout time, many published works have criticized the Japanese attack on Pearl Harbor on December 7, 1941, with many scholars attributing the attack to a failure of the United States of America’s military intelligence. Initially, this conclusion seems reasonable seeing as it is highly improbable that the United States military, one of the most advanced of its time, could neglect to realize that a Japanese force was advancing on the headquarters of its Pacific Naval fleet. An intelligence failure at Pearl Harbor was caused by the fact that Washington Navy and Army officials failed to properly distribute available intelligence, make educated decisions based on unevaluated intelligence reports, take every defensive measure when sources suggested a Japanese surprise attack and utilize all intelligence sources due to a heavy dependency on MAGIC intelligence. *

When countries want to communicate with foreign embassies they want to maintain security so that other countries are not aware of their political or militant intentions. They encrypt their communications. The US cracked the Japanese cipher which was code named purple, and began to listen in on diplomatic traffic. The translations of the information they gained from this traffic, they code-named MAGIC. *

* An important part of the United States intelligence gathering before December 7, 1941 was code-named MAGIC. MAGIC was highly classified diplomatic communication between the Japanese government and its foreign ambassadors and consulates. Once American cryptographers were able to decode this Japanese information, which was code-named “PURPLE”, listening stations in the Philippines and Hawaiian Islands were able to intercept, record, and translate entire messages. These translated messages then were then code-named and referred to by the United States of America as MAGIC. Obtaining MAGIC gave the United States an advantage when it came to negotiations between the two countries regarding the economic sanctions that the United States of America had placed on Japan. United States officials were able to pre-empt Tokyo’s negotiating strategy. Despite the advantages that MAGIC provided for the U.S. Army and Naval services, very few Washington officials had access to MAGIC intelligence. The Navy reported its intelligence to the following officials:

1. The Director of Naval Intelligence
2. Chief of the Far East section of the Office of Naval Intelligence (ONI)
3. Chief of the War Plans Section
4. Assistant Chief of Naval Operations
5. Chief of Naval Operations, Harold R. Stark
6. Secretary of the Navy
7. Naval Aid to the President
8. The President

The army’s signal intelligence was seen by:
1. Assistant chief of the G-2 staff
2. The Chief of War Plans
3. Chief of Staff
4. Secretary of War
5. Secretary of State

Only 13 Washington officials had access to MAGIC, making it extremely secure. Unfortunately, this meant that only one person could analyze the messages at a time, and: “It was, in effect, making each of the top officials his own intelligence officer… what he was receiving was raw, unevaluated intelligence. It had not been processed in any manner except for the decoding and translating….”

The varying analyses of MAGIC data complicated matters when it came to diplomatic relations with Japan: “Only if each of the recipients of “MAGIC” were an expert on Japan, knew the Japanese way of thinking…the relative power and ambitions of the army and the navy and the royal family…were aware of the vital needs of the economy for oil and raw materials…would it have been possible for him to convert the Japanese traffic into hard intelligence.”

Those translating MAGIC intelligence were not experts on any of these topics, and therefore Army and Navy officials interpreted and responded to intelligence to the best of their abilities. The failure of these leaders was not necessarily based on the decisions that they made as a result of their analysis, but the fact that their analysis was often faulty, as they knew little about the subject matter.

Due to the previously discussed rigid security surrounding MAGIC, many individuals who could have made use of this intelligence were denied it. Rear Admiral Edwin T. Layton was the Combat Intelligence Officer in charge of all intelligence related to the Pacific Fleet at Honolulu, and therefore should have had access to all Naval intelligence. Washington officials failed to grant him such access, as “[they] did not wholly trust the security arrangements of U.S. field commands…thus the reluctance to send massages to Hawaii or the Philippines.” In addition to this:

“The intelligence officer of the Pacific Fleet in Honolulu discovered that such messages existed and requested that copies be sent to him, but this request was turned down by Washington. The reason for the limited distribution was security.”

The fear that MAGIC information could be compromised by a security breech outweighed the logic of providing information to those officials that needed it the most.

Reliance on MAGIC as a main source of intelligence was also a failure of the United States of America’s leadership. * “It is most unlikely that anybody presumed to tell President Roosevelt or Harry Hopkins, or Secretaries Cordell Hull, Frank Knox or Henry L. Stimson, about what
information could or could not be obtained from communications intelligence, or that it was one source and should be evaluated in conjunction with all other available sources.” *

* Once cryptologists cracked the PURPLE code and began decoding MAGIC messages, Washington believed they had found their ace in the hole. However, the potential shortcomings of MAGIC were not properly addressed. As stated by __Lyman B. Kirkpatrick, Jr. in Captains Without Eyes: Intelligence Failures in World War II“…did they believe that the Japanese ambassadors in Washington would receive a message saying We are going to attack Pearl Harbor tomorrow at dawn?” In addition to this, W *

 * ashington’s dependency on MAGIC was so strong that they never considered the possibility that not all of Japan’s plans would be transmitted to their diplomats and that perhaps their diplomats were intentionally being kept in the dark. “The Americans did not appreciate that the two ambassadors in Washington…could be used as dupes… In fact, they knew little more about their country’s war plans than the Americans” Another example of MAGIC dependency came on Wednesday, November 26, 1941. Admiral Kimmel, Commander-in-Chief of the Pacific fleet based at Pearl Harbor, received a report that had been sent from the radio intelligence unit in Hawaii. It stated that a large concentration of Japanese submarines and carrier aircraft had amassed in the Marshall Islands. This likely meant that aircraft carriers were part of the group as well. Kimmel also received MAGIC intelligence messages that indicated that all Japanese carriers were in home waters.

Any indication of a militant Japanese force nearing an American Naval base should have been taken very seriously, however Kimmel ignorantly relied on MAGIC information, which did not indicate any reports of Japanese Naval activity in the Marshall Islands, and therefore no further investigation took place. It is likely that the Pearl Harbor attack could have been averted if it had. Another instance of MAGIC dependency occurred when Admiral Kimmel received a report that Japanese consuls in Far Eastern countries as well as in London and Washington had been ordered to destroy their secret documents and codes. Kimmel was also aware that the Japanese consulate in Honolulu was burning secret documents.

Kimmel ignored the local consulate’s actions based upon MAGIC reports ordering consulates in other locations to do the same thing. He felt that Japanese consulates were simply making preparation for Japan to end diplomatic negotiations with the United States. However, military officials have called the actions of local Japanese consulate an “unmistakeable tip-off”, because: “If you rupture diplomatic negotiations you do not necessarily have to burn your codes. The diplomats…can pack up their codes…and take them home. Also, when you rupture diplomatic negotiations, you do not rupture consular relations. The consuls stay on. Now in this particular set of dispatches that did not mean a rupture of diplomatic negotiations, it meant war…”

Admiral Ingersoll, who served as Commander-in-Chief of the United States Atlantic Fleet from 1942 to 1944, argued that Japanese consulates in Honolulu, London, and Washington were not preparing to end diplomatic relations. If that were the case, they would not need to be destroying their secret documents. His statement suggests that they were preparing for war. Admiral Kimmel failed to see this, and, as a result, the fleet at Pearl Harbor was not as prepared to defend itself. Another example of MAGIC reliance was found in regards to a message sent on November 15, 1941. The message ordered the Japanese consulate in Honolulu to increase the regularity of reports on the location of Pearl Harbor warships to twice a week.

Admiral Stark had received intelligence messages previous to this, the only difference being that Tokyo had requested that reports be sent more frequently, and that similar orders had been given to consulates located “on the West Coast and Panama.” Stark assumed that this request from Tokyo was simply an act of Japanese diligence and required no further attention. * Had Stark recognized that the request for more regular reports may have been related to the increased inter-country anxiety between Japan and the United States he may have been alerted to the possibility that Japan’s could attack Pearl Harbor. As a result of the reliance on MAGIC intelligence, as opposed to American messages, many essential defensive measures were not taken that could have prevented the disastrous battle at Pearl Harbor.

* General Walter Short was in charge of the Hawaii division of the American Army in 1941. The jobs of Short and Kimmel were intertwined – it was Short’s objective to protect the fleet at Pearl Harbor, while Admiral Kimmel was responsible for keeping the fleet battle ready at all times. Kimmel worked with Short in defence of the fleet and also provided long range reconnaissance. In conducting these tasks, both men failed to take every possible defensive measure when intelligence suggested the possibility of an attack on Pearl Harbor. Both Short and Kimmel knew that a war spurred by a Japanese attack was highly likely, and that it would most likely be a surprise. Kimmel himself wrote, “I feel that a surprise attack (submarine, air, or combined) on Pearl Harbor is a possibility.” Also, “The March 31, 1941, Martin-Bellinger Report likewise noted that “[i]n the past Orange [Japan] has never preceded hostile actions by a declaration of war.”

Both men were aware that on April 1st, 1941, Naval Intelligence in Washington alerted Hawaii that Axis Powers have often started attacks on either a Saturday or a Sunday, however,  “Although his men trained hard during the week, Kimmel kept a significantly lower state of readiness on weekends…” Ge

neral Short had also read the Martin-Bellinger report, and therefore was aware that a surprise attack was a possibility. On December 2nd, 1941, Lt.Cdr. Edwin T. Layton, Kimmel’s intelligence officer, briefed Admiral Kimmel that there had been no radio traffic from four Japanese aircraft carriers “for fully 15 and possibly 20 days”.The location of the four carriers was unknown. No further investigation took place. Both Kimmel and Short received messages from Washington on November 27th, 1941 warning that an aggressive move from Japan could occur “within the next few days”. Both Kimmel and Short knew that if Pearl Harbor was attacked, aircraft carriers were a possibility. As stated by the Secretary of the Navy to both Kimmel and Short: “The dangers envisaged in their order of importance and probability are considered to be:

1) Air bombing attack
2) Air torpedo attack
3) Sabotage
4) Submarine attack
5) Mining
6) Bombardment by gunfire”

Despite the notification by the Secretary that air bombing and air topedo attacks were considered top priority for defence, Kimmel issued orders to the fleet to “exercise extreme vigilance against submarines in operating areas…”. General Short ordered Alert Number 1, which was an alert against sabotage. Neither Short nor Kimmel took preparations to defend against the most likely form of Japanese attack: an attack from the air. Because of General Short’s emphasis on defence against sabotage, quick defence against an air attack was impossible. All of the ammunition for the anti-aircraft guns was under lock and key, meaning that no anti-aircraft guns were operational when Japanese planes began the attack. If Short and Kimmel had conducted their defensive measures based on the assessment sent to them from the Secretary of the Navy, the Pearl Harbor attack could have been better defended. Even Admiral Isoroku Yamamoto, the Commander-in-Chief of the Japanese Combined Naval Fleet, was prepared for far greater defensive measures than what Kimmel or Short had set up, as:

“Admiral Yamamoto expected his forces to be detected. In November 1941 he told…100 Japanese officers on the flight deck of the Akagi that although we hope to achieve surprise, everyone should be prepared for terrific American resistance…You may have to fight your way in…”

Short and Kimmel knew a number of things that should have spurred them to take greater defensive action against the possibility of attack, yet both men failed to institute a proper level of defensive alertness based on the information they had.

The attack at Pearl Harbor has often been attributed to an intelligence failure. This is correct, however Japan and the U.S. were on a crash course with each other as a result of a failure to step away from their ingrained policies and beliefs. “The Japanese were determined to pursue their imperial ambitions in the Pacific, and the Americans were determined to stop them.” When the diplomats of either country were committed to these policies and courses of action, there is little that signals intelligence or MAGIC could have done other than listen to how those actions or policies ran their course. Intelligence could only count down until the Pacific War began; it was inevitable. What was not inevitable was Washington’s failure to properly distribute intelligence that was available due to rigid security measures.

Because Washington received raw, unevaluated intelligence reports, its officials had to analyze it themselves, which created multiple one-person intelligence agencies. This meant decisions had to be made based on material that certain officials knew little or nothing about. Army and Navy officials failed to take every possible defensive measure when multiple sources suggested that a Japanese surprise attack was a possibility. The U.S. government failed in the sense that it developed a heavy dependency on MAGIC intelligence, and in doing so did not give other intelligence sources the attention that they required. After investigating these failures it is clear that although War in the Pacific was inevitable, the devastation of the December 7th, 1941 attack on Pearl Harbor was not.

Works Cited

Alvarez, David J.. Secret messages: codebreaking and American diplomacy, 1930-1945. Lawrence, KS: University Press of Kansas, 2000. Borch, Frederic L., and Daniel Martinez. Kimmel, Short, and Pearl Harbor: the final report revealed. Annapolis, Md.: Naval Institute Press, 2005. Dupuy, Colonel T.N.. “Pearl Harbor: Who Blundered? | American History Lives at American Heritage .” American History Lives at American Heritage . http://www.americanheritage.com/content/pearl-harbor-who-blundered (accessed November 8, 2012). Kirkpatrick, Lyman B.. Captains without eyes; intelligence failures in World War II. New York: Macmillan, 1969. Wohlstetter, Roberta. Pearl Harbor; warning and decision. Stanford, Calif.: Stanford University Press, 1962.

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