Intelligence

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. 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. 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 little of this information was passed on to the powers at war with Japan.

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 turned the other way. Closely related to coast watchers, and sometimes synonymous with them, were various guerrilla organizations, which were particularly active in the Philippines. Philippine guerrillas actually 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.

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, 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.

More 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.

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 story. The Allies devoted considerable resources to analysis of information 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.

Counterintelligence

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. Counterespionage was less prominent in the Pacific, where the Japanese breaking of the Sorge ring was about the only important counterespionage success on either side.

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. 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.

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

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. 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.

Japanese 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.

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