Through intercept, cryptanalysis and translation of Japanese messages, Communication Intelligence (COMINT) supplied decision makers with a continuous flow of information on Japanese naval and merchant shipping, convoy routing and composition of forces along with a wealth of other pertinent intelligence. Below is a time-line of success and tragedies that is part of our Naval COMINT history.December 7, 1941: 51 days after Corregidor was operational, Japanese attacked Pearl Harbor.

December 8, 1941: All eight intercept operators on Guam were taken prisoner by the Japanese.

December 1941 – April 1942: Communications Radio Intelligence Unit, Corregidor were ordered to evacuate at Luzon, Philippines.

December 31, 1941: YN3c Kenneth F. Grisham was crushed to death by an overturned tractor shortly after the first bombing attack on Corregidor.

During WW II, the U.S. Navy Radio Station operations at Bainbridge Island, WA comprised of Supplementary Station that included a Communications Technician (CT) intercept School.

February 4, 1942: USS SEADRAGON (SS 194) evacuated first group at Corregidor.

March 16, 1942: USS PERMIT (SS 178) evacuate second group at Corregidor.

April 8: USS SEADRAGON (SS 194) evacuated third and final Group at Corregidor.

April 17, 1942: StationHYPO intercepts Japanese plans to attack Port Moresby.

May 1942: 01 November 1945: Communications Radio Intelligence Unit, Melbourne was established.

May 3, 1942: Battle of Coral Sea was the first major engagement between U.S. and Japanese forces where not in visual range. Station Hypo directly attributed by tracking the Japanese naval forces. The battle gave Admiral Nimitz confidence in COMINT.

June 4-7, 1942: Battle of Midway – Due to the cryptologic achievements of CDR Rochefort and his staff, ADM Nimitz knew that the attack on Midway would commence on June 4. Armed with this crucial information, he was able to get his outgunned but determined force in position in time.

September 1942: School facilities at Bainbridge enlarged to accommodate 100 men.

September 1942: School facilities at Cheltenham enlarged to accommodate 75 men.

February 7, 1943: Communications Security Group transferred to Mt. Vernon Academy on 3801 Nebraska Ave. NW, Washington, DC.

April 1943: $475,000 was authorized for enlargement for intercept facilities at Wahiawa.

April 18, 1943: Admiral Yamomoto Shoot Down. Naval intelligence intercepted and decrypted a message containing specific details regarding Admiral Yamamoto’s flight plans from Rabaul to Ballalae airfield. As a result, a U.S. Army P-38G fighter shot down the aircraft Yamomoto was flying in.

June, 1943: Based on COMINT reporting USS TRIGGER (SS 237) inflicted severe damage to the Japanese carrier Hitaka (or Hiyo), which put her out of commission for almost a year.

August 1943: Analysis of the activities carried out by OP-20-G was conducted and the first effort to establish a rating for Communications Intelligence Enlisted Personnel was initiated.

August, 1943: Based on COMINT reporting USS POGY (SS 266) sank Mogamigawa, a Japanese aircraft transport.

September 1, 1943: The first of 200 Bombe machines were shipped to U.S. Navy’s Nebraska Avenue Building in Washington, DC. A BOMBE was a large electro-mechanical machine used to recover the keys used by German ENIGMA cipher machines.

November 1943 – February 1944: Battle of the Marshals and Gilbert Islands was the first time COMINT was used to direct ground forces.

December, 1943: Based on COMINT reporting USS SAILFISH (SS 192) sank Chuyo, a Japanese escort carrier.

March, 1944: Based on COMINT reporting USS TUNNY (SS 282) sank the Japanese submarine I-42

June 1944: Based on COMINT reporting USS PINTADO (SS 387) and USS SHARK II (SS 314) destroyed a large Saipan-bound convoy by just prior to U.S. forces landing on the island.

July, 1944: Based on COMINT reporting USS SAWFISH (SS 276) sank the Japanese submarine I-29.

7 July 1944: RM2c Lyle J. Jansen and RM2c Robert J. Lynch were both KIA in Kwelin, China.

July 10, 1944: High quality COMINT reporting provided information to decision makers in support of the New Guinea campaign.

31 July 1944: LT Walter S. Gifford, and LTJG Delbert Gideon were KIA at Funafuti Lagoon, Funafuti Island, in the South Pacific.

September, 1944: Based on COMINT reporting USS SEA DEVIL (SS 400) sank the Japanese submarine I-41

23 September 1944: U.S. Marine intercept operators CPL Joseph A. Prete, CPL Stephen J. Weber, and PFC William Hughes, Jr., were KIA at Peleiu Island, Palau Group, Carolina Islands.

November, 1944: Based on COMINT reporting USS SPADEFISH (SS 411) sank the Japanese Jinyo, an escort carrier Jinyo.

December, 1944: Based on COMINT reporting USS REDFISH (SS 359) sank Unryu a Japanese of carrier.

December, 1944: Based on COMINT reporting USS REDFISH (SS 359 and/or USS SEA DEVIL (SS 400) severely damaged the Japanese carrier Hayataka (or Junyo), which put her out of commission for remainder of war.

February, 1945: Based on COMINT reporting USS BATFISH (SS 310) sank Japanese submarines RO-115, RO-112 and RO-113 within four days.

April, 1945: Based on COMINT reporting USS SEA OWL (SS 405) sank Japanese submarine RO-56 near Wake Island.

April, 1945: Based on COMINT reporting USS CHARR (SS 328) sank the Japanese light cruiser Isuzu.

April 7, 1945: COMINT reporting provided information that resulted in the attack and sinking of the Japanese Battleship Yamato near Okinawa.

April, 1945: Based on COMINT reporting, USS THREADFIN (SS 410) and USS HACKLEBACK locate and track the Yamato task force. This resulted in sinkings the following day by carrier air forces of the battleship Yamato, the cruiser Yahabi, and destroyers Hamakaze, Isokaze,Asashino and Kasumi.

12 May 1945: RM1c Walter L. Rougeux, USN was KIA onboard the battleship USS NEW MEXICO (BB-40) as the result of a Kamikaze crash.


A letter dated June 17, 1947, from VADM C. A. Lockwood to the CNO, the Commander make if a matter of record the role COMINT played during WWII:

“As Commander of the Submarine Force, U.S. Pacific Fleet, from February, 1943, through the end of hostilities, I can vouch for the very important part which Communication Intelligence played in the success of the submarine campaign.

The contribution to the defeat of Japan in World War II by United States submarines is a matter of record. More than two-thirds of the entire Japanese merchant marine and numerous warships, including some of every category, were sunk. These sinkings resulted, by mid-1944, in isolation of Japan from her overseas sources of raw materials and petroleum, with far reaching effects on the capability of her war industry to produce and her armed forces to operate. Her outlaying bases were weakened by lack of reinforcements and supplies and fell victim to our air, surface and amphibious assaults; heavy bombers moved in to the captured bases and decimated and demoralized the Japanese to the point where they were forced to accept unconditional surrender. These effects of submarine operations have been substantiated, both from Japanese and Allied official records, and for the most part have been made public in detail, but nothing has been told about the manner in which such outstanding results were achieved by such a relatively small submarine organization.

The information furnished made possible the assignment of submarines not only to the most profitable patrol areas but also to specific locations at particular times where contacts were made with convoys of known composition and importance, and frequently with enemy course and speed known exactly. Combatant units of the Japanese Fleet were similarly located on many occasions. During periods, which fortunately were brief, when enemy code changes temporarily cut off the supply of Communication Intelligence, its absence was keenly felt. The curve of enemy contacts and of consequent sinkings almost exactly paralleled the curve of volume of Communication Intelligence available. There were many periods when every available submarine on patrol in the Pacific Ocean Area was busy on information supplied by Communication Intelligence. The vast reaches of the Pacific Ocean could not otherwise have been covered so thoroughly unless a far greater number of submarines had been available. In early 1945 it was learned from a Japanese prisoner-of-war that it was a common saying in Singapore that you could walk from that port to Japan on American periscopes. This feeling among the Japanese was undoubtedly created, not by the great number of submarines on patrol, but rather by the fact, thanks to Communication Intelligence, the submarines were always at the same place as Japanese ships.”

August 15, 1945: Surrender of Imperial Japan was announced

Multiple sources