By mid-1942, it became evident that a separate intelligence organization was needed to correlate and publish the vast quantity of intelligence material necessary to support offensive operations. There was no organization to produce the great volume of maps, charts, information booklets, and data on enemy material and general information on the enemy. In September 1942, a separate Intelligence Center, Pacific Ocean Area (ICPOA) was established with Hypo’s Combat Intelligence Center as one of its supporting organizations. The new intelligence center established an Objective Data Section, an Air Intelligence Section, and other sections as capabilities permitted. By April 1943, both the CIC and ICPOA had outgrown their quarters in the basement of the Administrative Building, Pearl Harbor and they moved to a new building at Makalapa along with FRUPAC. Certain function such as a daily plot of all enemy naval and merchant vessels, contact reports, important HFDF fixes, and the general major movements of U.S. forces were maintained by ICPOA but were available for radio intelligence personnel.
On 7 September
1943, ICPOA became the Joint Intelligence Center Pacific Ocean Area (JICPOA)
under Colonel (later Brigadier General) J. J. Twitty, USA.
The close relationship between CIC and ICPOA continued under the new organization
and both grew tremendously to meet the ever-increasing intelligence requirements
of offensive operations. CIC had four watch officers with private
and secure communications with the Fleet Intelligence Section, ComSubPac
and all sections of radio intelligence. They also produced the “daily
book” of all radio intelligence for CinCPac, researched CinCPac requests
and acted as coordinators in intelligence exchanges between all parties.
Each watch officer specialized in one field such as destroyers, submarines,
merchant ships and their studies were the basis of the “Weekly Estimate
of Locations of Japanese Naval Vessels” and “Estimate of the Enemy Intentions.”
The head of the air section of ICPOA/JICPOA spent a large portion of his
time in CIC preparing the “Weekly Estimate of Location of Japanese Air
Forces.” The head of the land forces of ICPOA/JICPOA performed a
similar service concerning Japanese land forces.
Station Hypo became known as the Fleet Radio Unit Pacific (FRUPAC) to the outside world and its jurisdiction was changed from intelligence to communications through the efforts of the new regime at OP-20-G. However, it continued its close cooperation with JICPOA and its own Combat Intelligence personnel who were absorbed into JICPOA.
Theater intelligence activity included the progressive collection of photographs of objectives, several hundred miles in advance of secured bases. This was evaluated with other source material within our control such as captured documents, prisoner interrogations, etc. In advance photographic missions, the reconnaissance of submarines proved to be most useful. Their photographs proved invaluable for surface approach in operations and for the selection of landmarks.
During the planning for the Gilberts campaign, CIC acted as the information agency for the CinCPac War Plans. However, for the Marshal's campaign, a formal Estimate of the Enemy Situation was produced early in the planning stages. This was supplemented by a special modifying report deadlined as close as possible to the sailing date of the operational forces. This system was continued throughout the war for all major campaigns and strikes.
Early in 1944 considerable information had been collected on enemy mine warfare. Therefore, a mine warfare officer was added to CIC and this assisted radio intelligence’s recovery of enemy mine information that was especially valuable initially to Allied submarine operations, but as the war closed in on Japan home waters it became of utmost importance to all operational forces. About the same time, an officer responsible solely for Japanese submarine warfare was added. Allied convoys were rerouted to avoid Japanese submarines as well as directing submarines to intercept IJN combatants whose movements were seen in decrypts.
Prior to 1944, there was little Army participation in CIC, although some of JICPOA’s products were distributed to Army forces. After the Marianas campaign, it was realized that enemy air estimates required full information on Japanese Army Air Forces deployments. The first Army contingent consisted of four officers. Three took over the preparation of the Weekly Estimate of Japanese Land Forces, while the fourth worked on Japanese Army Air Forces and assisted in the Weekly Air Estimates. Special communications were set up for Army personnel with the Special Branch War Department G-2 to check, verify, or amplify intelligence required for estimates or to conduct special research.
A relationship between COMINCH’s F-22 Combat Intelligence section was established and personnel were exchanged on a temporary duty basis, with some F-22 trained officers being sent to Pearl.
JICPOA also acted as an advanced training base for ten to fifteen graduates of the Advanced Naval Intelligence School. Many future fleet intelligence officers were taken from this pool that was established at JICPOA.
In early 1945, planning commenced for B-29’s to mine Empire waters. Special reports were sent to the 21st Bomber Command to assist them in the selection of mining targets and in the evaluation of mining efforts. A weekly mine warfare report was established to report on the ships sunk or damaged, effectiveness of sweeping operations and other mine information. This report became in demand by other commands besides the 21st Bomber Command and eventually became a targeting type report.
Dissemination of publications, maps and charts, terrain models, and many other products to agencies outside the CinCPac area was extensive. Millions of propaganda leaflets and bulletins were sent to the Sixth Army and other forces for use in the Philippines. JICPOA supplied twenty-two tons of intelligence material for the use in the recapture of Leyte. A total of nearly one hundred twenty five tons was contributed to the recapture of the Philippines. Much intelligence information was supplied to the U.S. Strategic Air Forces.
In April 1945, certain operation type intelligence efforts were established at Ragfor Guam. This move became necessary to properly use Japanese naval traffic being intercepted at Guam and available there before it was at Pearl.
When the operational control of the British Pacific Fleet was assigned to CinCPAC in 1945, intelligence was supplied to them on the same basis as for the U.S. Pacific Fleet.