Navy History and Heritage Command #NH 84826
Military intelligence is that branch of the
military art concerned with deducing the enemy's dispositions,
capabilities, and intentions. It includes both data collection and
analysis. The Japanese started the
Pacific War with a significant advantage in intelligence, but rapidly
fell behind the Allies,
primarily due to superior Allied cryptanalysis.
Data came from many sources. Traditional human intelligence, otherwise known as espionage, played an important role for the Japanese as war approached. Japanese consulates in target areas assiduously collected information and passed it back to Japan for war planning purposes. Japanese "tourists" were also active, and Japanese fishing vessels conducted extensive hydrographic surveys of potential landing areas. When the Taiyo Maru arrived at Honolulu on 1 November 1941, it carried three Japanese intelligence agents who managed to smuggle reports from the consulate on board and who made extensive observations of air and sea activity around Oahu. Asaka Maru carried out a similar mission to the Panama Canal and Germany in early 1941. British prisoners of war at Hong Kong recognized one of their captors as a former barber in the British barracks, and natives on Guadalcanal recognized a Japanese officer, "Ishimoto", as a former itinerant carpenter at Tulagi. These spies turned occupation officers were often most brutal towards those they had formerly spied upon. For instance, "Ishimoto" is alleged to have arrested and murdered two Roman Catholic priests and two nuns from Ruavato mission.
Many of these sources
dried up once war broke
out. The Japanese attempted to organize a spy ring on Oahu to replace
intelligence gathering by the Honolulu consulate, but the leader of the
ring, Otto Kuehn, a German
national, was unfit by training
and temperament to be an effective spy, and the FBI arrested him the
day after the attack on Pearl
Harbor. However, Axis
agents
remained active in Noumea,
the Allies recruited a number of Thai
agents in southeast Asia, and pretty much everyone spied on everyone
else in China. The Sorge ring in Tokyo provided some excellent
intelligence to Russia, but this
information was not passed on to the powers at war with Japan.
No one was better than the Russians in human
intelligence. Not only did Russian agents penetrate the German and
Japanese governments, but there were an estimated 329 Soviet agents
within the U.S. government, including Roosevelt's senior
economic advisor, Lauchlin Currie; assistant Treasury
secretary Harry Dexter White; and Bill Donovan's personal assistant at
OSS, Duncan Chapin Lee. The British
government was at least as heavily penetrated, including by the
"Cambridge Five." Intelligence supplied by these agents doubtless
played a role in the end game in the Pacific.
Another source of human intelligence used by both sides was coast watchers. These were agents left in the jungle in areas overrun by the enemy. The Australian "Ferdinand" organization, which operated in the Solomons and New Guinea, was particularly famous, but the Japanese also employed coast watchers once the tide had turned. Closely related to coast watchers, and sometimes synonymous with them, were various guerrilla organizations, which were particularly active in the Philippines. Philippine guerrillas succeeded in capturing Fukudome Shigeru, chief of staff of Combined Fleet, after his plane crashed in a typhoon in mid-1944. He was released out of fear of reprisals, but the documents he was carrying found their way to Allied headquarters.
Another form of human intelligence was
interrogation of prisoners of
war. The Geneva
Convention required prisoners of war to give basic identifying
information ("name, rank, and serial number") but forbade interrogation
under duress. The Japanese ignored
this convention and employed both physical and psychological torture,
occasionally obtaining important information. For example, at Midway, an American pilot
threatened with execution gave the Japanese a fairly complete order of
battle for U.S. forces, including sailing dates that might have given
away the fact that the Americans were reading the Japanese codes.
Fortunately for the Allies, the Japanese failed to make the connection.
The pilot was subsequently murdered in spite of his cooperation.
Fear of interrogation under torture led to strict
rules for employment
of personnel who were privy to the most sensitive Allied intelligence.
High-ranking officers who were cleared for cryptanalytic data ("Ultra")
were kept from situations in which they might be captured. Junior
intelligence officers were almost never permitted to transfer to
front-line duty. Joseph Rochefort (pictured above), who led the
cryptanalysts during the
crucial Coral Sea-Midway period,
was given command of a floating
dry dock when he requested a sea assignment; this looked like a
calculated insult, but it probably reflected the fear that
he might be captured and tortured by the Japanese if assigned to a
warship. Captain John
Cromwell unwisely led a submarine
wolf pack off the Gilbert
Islands in spite of
his knowledge of Ultra, and when his pennant submarine was crippled, he
chose to go down with the boat
rather than risk capture and
interrogation. He was subsequently awarded the Medal of Honor for his
sacrifice.
Allied interrogators did not as a rule employ any form of torture. They did not need to. Because the Japanese military code of honor absolutely forbade surrender, Japanese soldiers received no instruction on how to behave in captivity, and those captured felt such shame that they had little psychological resistance to interrogation. Many sang like canaries. However, the fact that officers almost never surrendered meant that almost all prisoners were enlisted men with little or no high-level information to impart.
The need for skillful interrogation was not
limited to prisoners of war. Friendly local civilians were
sometimes important sources of information, though such civilians
risked being treated as spies if they crossed enemy lines.
Interrogation of one's own pilots
and soldiers returning from sorties and patrols (debriefing) was an
important aspect of intelligence, and one sometimes requiring
considerable tact and skill. Pilots on all sides tended to greatly
overestimate their own effectiveness in combat, claiming far too many
kills of enemy aircraft
and far too much damage to enemy shipping. Because the Allies had
access to other superb sources of intelligence, they were able to
confirm the survival of many ships thought by attacking pilots to have
sunk. Allied intelligence officers came to be skeptical of claims of
aircraft kills as well, and began to require kills to be confirmed by
gun cameras or a second pilot. The Japanese were far less careful about
damage assessment, and grossly inflated claims of ships sunk and
aircraft destroyed characterized Japanese battle damage assessment
throughout the war. This often led the Japanese to adopt unrealistic
courses of action, such as the order to Shima to mop up 3 Fleet after it was
supposedly shattered off Formosa
in the fall of 1944.
Also important for the Allies was the capture of
documents. Allied divers became proficient at recovering
important
documents from wrecked ships,
including very sensitive documents
recovered from the sunken cruiser
Nachi
in Manila harbor. Documents were
also recovered from overrun Japanese positions. In one famous incident,
a Japanese commander in New Guinea
buried a cache of code books rather than burning them, and they were
discovered by Allied forces, giving a tremendous boost to
cryptanalysts. Diaries recovered from Japanese bodies had considerable
intelligence value, though sometimes it was difficult to get Allied
combat
troops to give up their "souvenirs." The Allies actively
discouraged their own men from keeping diaries, though individuals like
Eugene
Sledge (With The Old Breed)
and James Fahey (Pacific War Diary)
found ways to surreptitiously record their experiences, to the delight
of later historians.
Capture of documents was not a purely wartime
activity. U.S. Navy Intelligence burgled the Japanese Consulate in New
York to obtain vital cryptographic information. This proved so valuable
that the Navy Department persuaded the State Department to leave
Japanese consulates open when the German consulates were closed on 10
July 1941.
The Japanese also made use of captured documents.
On 11 November 1940 the German merchant raider Atlantis captured the British cargo
liner Automedon off Sumatra. The British ship was
carrying a number of very high-level dispatches to Commander in Chief, Far East,
which the crew were unable to destroy before they could be seized by
the German boarding party. The Germans turned the documents over to the
Japanese at Tokyo. The documents
laid bare Britain's weakness in the Far East, particularly her
inability to hold Hong Kong in
the event of war with Japan.
Reconnaissance was another important form of intelligence. Tactical reconnaissance consisted of patrols in land combat and of air searches in naval combat. The Japanese debacle at Midway was partially a consequence of ineffective air search. Strategic reconnaissance could be conducted by submarines or by long-range aircraft equipped with special cameras.
Radio intelligence was decisive to the course of the conflict. Traffic analysis is the art of deducing enemy dispositions from the pattern of radio signals and was practiced with success by both sides. Cryptanalysis, the actual decoding of enemy signals, was practiced most successfully by the Allies, though the Japanese did succeed in breaking some low-level codes, such as those used to transmit weather reports.
Collection of data was only half the intelligence story. The Allies devoted considerable resources to analysis and had a clear edge over the Japanese in this area. One consequence was the Japanese failure to deduce that their codes were being read, in spite of several glaring slips by the Allies. But even Allied intelligence could occasionally go wrong. A mistaken deduction about Japanese intentions in March 1943 led Ralph Christie to order the west coast of Australia cleared of shipping in anticipation of a carrier raid that never materialized. Ironically, documents from Fukudome's captured briefcase (mentioned above) led Spruance to believe that the Japanese might attempt an "end run" at the Battle of the Philippine Sea, which makes his cautious strategy in that battle easier to understand.
Analysis can be broken down further into capabilities and intentions. Capabilities are relatively easy to deduce, since (in principle) their deduction is a straightforward mathematical exercise. Intentions are much more difficult, and it has long been a military maxim to base one's strategy on what the enemy is capable of doing, rather than what you think he intends to do. However, the Allied success in cryptanalysis often revealed enemy intentions as well as capabilities.
Good analysis requires getting into the enemy's mind. Allied contempt for the Japanese hindered this process before war broke out, most spectacularly at Pearl Harbor. The shock of that debacle led to improved analysis. The Japanese, in turn, misread the Americans because of their own contempt for such a "soft" race. The most important example was the failure to appreciate how the Pearl Harbor attack would infuriate the Americans and make a negotiated peace impossible. This is particularly surprising, since the chief advocate of the Pearl Harbor attack, Yamamoto, had spent considerable time in America. On a tactical level, the assumption that Americans were soft led Japanese intelligence to grossly underestimate how many Marines had landed on Guadalcanal. The Japanese assumed that the American desire for "the amenities" meant that twenty transports were required to carry an American regiment, when in fact the 23 transports off Guadalcanal had brought in a full division.
Strategic radio intelligence was complemented by
battle intelligence. Following the failure of the Wake relief effort in December 1941, Fletcher asked that his task
force be assigned "specially trained radiomen to copy Japanese sending,
and specially trained officers to interpret was is being intercepted"
(Lundstrom 2006). He received a Marine
captain fluent in Japanese in January, and shortly thereafter Nimitz assigned a radio
intelligence team to each carrier task force. These proved increasingly
effective as the war went on. At the Battle of the Philippine Sea, the
intelligence team was able to obtain such useful information from
monitoring the Japanese strike leader that they humorously requested
that the combat air patrol not shoot him down at the end of the
engagement, as he had served the Americans so well.
Just as military forces seek intelligence concerning the enemy, they also seek to deny the enemy intelligence about themselves. There are basically three ways to do this. The first is to damage the enemy's intelligence collection apparatus. The second is to reduce one's own information signature. The third is to swamp one's own information signature with false information.
Counterespionage is basically detective work to identify spies. It relies heavily on leads from ordinary soldiers and citizens who think they have seen something odd. Since the overwhelming majority of leads go nowhere, this is dull, grinding work, contrary to the glamorous James Bond image. It could also be an ugly business, as spies enjoy little protection under international law and espionage during the war years was universally regarded as a capital offense. The Allies were remarkably successful at counterespionage in the European theater, where it appears that every agent the Germans attempted to infiltrate into Britain was immediately arrested and forced either to "turn" or be executed by hanging. Allied counterespionage was less prominent in the Pacific, but the Japanese breaking of the Sorge ring was a major scandal, while the Kempeitai broke a spy ring in a Hong Kong prisoner of war camp and other spy rings in the Netherlands East Indies and the Philippines.
Counterespionage overlaps counterinsurgency when guerrillas serve as a source of intelligence. The Japanese success in counterespionage in the Philippines closely correlated with their success in counterinsurgency.
Screening
is the process of foiling enemy reconnaissance. The most obvious form
of screening is to intercept and destroy the reconnaissance unit. This
is sometimes harder than it would appear. Reconnaissance aircraft were
designed for high speed and approached at high altitude, making them
difficult to intercept. Submarines on reconnaissance missions were
almost impossible to thwart, since they could choose the time and place
to expose themselves. Infantry
patrols were easier to defeat: Effective
patrolling requires skill and nerve, and patrols could be thwarted by
constructing obstacles, such as barbed wire or minefields, or by
deploying listening posts or noisemakers. A favorite technique of the Marines was to hang empty tin
cans with pebbles on barbed wire in front of their lines. These created
noise if the barbed wire was disturbed by infiltrators.
Operational security is the art of reducing one's own intelligence signal. Means for accomplishing this included maintaining radio silence whenever possible; using means other than radio to communicate sensitive messages; using various forms of camouflage to evade or confuse enemy reconnaissance; and limiting information to those with a strict need for the information. Allied personnel were discouraged from keeping diaries, and deploying soldiers and sailors were not told their destination until they were already at sea.
Deception
is the art of contriving false or misleading information that is
sufficiently convincing to fool the enemy. Since enemy intelligence is
likely already flooded with a mass of observations, from which they
must somehow sift the few observations of real value, one need not
plant much false information to make the enemy's task harder. However,
there is always the risk that the deception will be detected and give
the enemy genuine clues to one's own intentions. This risk can be
minimized by planting some true but out of date or otherwise useless
information in order to give the sources of false information greater
credibility.
Sources of false information during the Pacific
War
included simulated radio traffic to mislead enemy traffic analysis;
deployment of dummy aircraft or tanks
to attract the attention of enemy
reconnaissance; and use of double agents to return false or misleading
human intelligence. In November 1941, the Japanese Navy redeployed a
replacement air group to the bases vacated by the Pearl
Harbor strike force, granted shore leave to as many sailors as
possible, and had the replacement air group send out dummy messages to
conceal the sailing of the strike force. Allied troops headed for the Aleutians were lecture on
tropical diseases and senior
officers allowed themselves to be seen
studying charts of the Atlantic or the Argentine coast in hopes of
planting false rumors about their destination.
One form of deception is the Haversack Deception,
in which faked documents are planted where they will be discovered by
the enemy. The Allies had great success in Europe with Operation
Mincemeat, in which a dead body was floated ashore in Spain dressed as
a Royal Marines officer and bearing a suitcase full of documents
suggesting an Allied assault on Greece. This successfully drew Axis
attention away from Sicily, where the real assault was planned, with
the added bonus that genuine documents captured later in the war were
discounted by the Germans as plants. No such success was achieved in
the Pacific, in spite of efforts such as leaving a wrecked jeep
containing fake documents in the path of the Japanese advance in Burma. The Japanese simply ignored the
wreckage.
The best deception schemes played to the enemy's prejudices, and if one's own intelligence service was reading enemy codes, it was possible to closely monitor the effect that deception schemes were having on the enemy's thinking and adjust accordingly.
Allied intelligence benefited tremendously from the efforts of cryptanalysts. However, this was only one element of a comprehensive intelligence program that gave equal weight to information gathering and analysis. The Joint Intelligence Center, Pacific Ocean Areas (JICPOA) eventually had a strength of 1,767 specialists drawn from all branches of the armed forces. MacArthur received valuable intelligence from the Central Bureau, a joint American-Australian organization, and 7 Fleet's Fleet Intelligence Unit Melbourne (FRUMEL). When changes to Japanese codes temporarily thwarted the cryptanalysts, the intelligence community fell back on traffic analysis. This information was supplemented with direct reconnaissance from submarines and long-range reconnaissance aircraft.
The Allies took considerable pains to conceal their signals
intelligence from Japanese counterintelligence. However, there were
occasional blunders in the war which the Japanese failed to exploit.
Sensitive intelligence was much too widely disseminated until after the
Battle of Midway, as when Spruance
announced to his task force that a Japanese admiral was thought to be present
on a "battleship" (actually heavy cruiser Mikuma)
that was about to be attacked. The announcement was intended to raise morale, but was a textbook example of
too wide dissemination of (in this case faulty) intelligence.
Once the war was well underway, Japanese intelligence fell badly behind the Allies. The situation was summarized by a staff officer in the intelligence section of South Asian Army (Hastings 2007):
Only in 1944 did the war situation really begin to alarm us. The Japanese army did not take intelligence nearly seriously enough. At South Asia Army HQ, we had no proper system, no analytical section, no resources -- that's how bad it was. Perhaps our attitude reflected Japan's historic isolation from the rest of the world. We had no tradition of being interested in other societies and what they were doing. It came as a shock to realize how powerful the Allies were becoming, and how much they they knew about our actions and intentions.
Historian Hando Kazutoshi added (op. cit.):
Intelligence became a backwater for officers who were perceived as unfit for more responsible postings. Strategic decision-making was concentrated in the hands of perhaps twenty people, military and naval. Even if our intelligence services had gained access to important information, it would have remained unexploited if it ran against the convictions of the decision makers. They would not have wanted to know.
The Japanese Navy was no better. It had no intelligence school
before war broke out nor any courses on intelligence in its other
schools. Funding and manpower were completely inadequate under wartime
conditions. Japanese intelligence officers attributed this to the ease
with which the open U.S. society was penetrated in peacetime, which led
to complacence.
The Japanese conducted peacetime espionage from their consulates and
embassies, but also put in place "sleeper" organizations with no
connection to consulates to be activated in time of war. Espionage from
the Japanese consulate on Oahu was
highly effective, but the local sleeper organization proved almost
completely ineffective once war broke out and was rapidly rolled up by
the FBI.
References
Federal Bureau of Investigation Website (accessed 2009-12-17)
The Pacific War Online Encyclopedia © 2007-2010 by Kent G. Budge. Index
