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Historical Events
Historical Events | Aug. 20, 2021

COMINT Stations Overseas

As early as 1924, the Navy established intercept sites in China and Oahu to copy Japanese communications -- the Shanghai station, established in 1924 may have been the Navy's earliest shore-based intercept site, with Wailupe, Hawaii second in 1925, and then Peiping [Peking] in 1927. Some intercept activity was also carried on in Guam, and San Francisco, and aboard the USS Huron.

The motive for establishing field stations in Hawaii was the need for an intermediate site to receive and do initial processing on intercept copy. Originally, copies of intercept had to be forwarded by officer courier, later by air mail, but, under either system, most intercept was badly outdated by the time it reached Washington.

The island of Guam became host to a one-person intercept site in March 1929, when a single operator was transferred from a site in China. Within a year, the lone interceptor was joined by seven graduates of the Washington training program. Although there were frequent requests to build up the personnel strength of the site, the number of operators remained +/- 10 until the beginning of the war.

The intercept operators' experience at the station at Guam illustrates some of the non-technical difficulties COMINT personnel faced. The operations building had been built of coral mortar blocks by the Spanish prior to 1898. When it was occupied in 1929, the building's floor was rotting. The damp and humidity meant that paper and equipment mildewed rapidly. The Navy's own radio transmissions from Guam interfered with intercept. Eventually, the collection site was moved to an abandoned hospital where conditions were somewhat better.

By 1934, in the Philippines, it became apparent that Olongapo was inadequate as an intercept site. Although high-level approval by the Army command in Washington was given for the Navy to move to Corregidor, local authorities demurred. The local Army commander intended to install a Signal Corps unit there, and complained that the higher pay scale of Navy operators would create morale problems for his men. Arrangements were made then in 1935 to transfer the Navy site to Cavite, where it would also be protected by the fortress island of Corregidor.

After negotiations at high levels with the Army, which administered the Philippines, a tunnel for Navy intercept was constructed on the island of Corregidor itself. Personnel of Station C (or Station CAST) occupied it in October 1939.

The Radio Security Station in Peking [for internal Chinese political reasons, Peking was known as Peiping in the late 1920s], was tasked with intercepting Japanese diplomatic material on behalf of OP-20-G, and with providing current intelligence to the Asiatic Fleet. The site had both Navy and USMC enlisted personnel assigned.

The Peking site provided excellent coverage of the crisis in Manchuria in 1931, when the Japanese Army staged a coup and detached that mineral-rich area from central Chinese control. The relative closeness of the fighting and the unrest it caused, however, led to fears that the station, along with the U.S. legation might be vulnerable, and Navy officials began thinking about relocating the site.

The original intercept site at Peiping was in a poor position from a local security standpoint, anyway. Only a low wall separated it from a main highway. One veteran remembered that on hot nights the operators had to open windows for ventilation and then keep the power low on their receivers to prevent passers-by from overhearing the radio traffic.

The Navy site at Peiping was closed in July 1935, and operations transferred to Shanghai. This was done primarily for security and to expedite the transport of intercept. There had been a shore-based site at Shanghai as early as 1924, but its operations had been shifted to the USS GENERAL ALAVA in 1927; two years later that operation was disestablished. The Shanghai site was staffed by Marine Corps intercept operators until 1937, when Navy personnel came in as replacements. Station commanders, however, continued to be Marine captains.

The station at Shanghai was itself closed in December 1940, and operations shifted to Cavite in the Philippines.

Among those who served at the Peiping and Shanghai stations was Stephen Lesko. As a Marine Corps private, Lesko had volunteered for intercept duties, been given on-the-job training in copying Japanese messages, and assigned over the years to a number of stations around the Pacific. During World War II, as a lieutenant, Lesko helped organize Marine intercept units for direct support to combat operations. Lesko retired as a lieutenant colonel.

The overseas stations took on simple covernames: HYPO became the designation for the Navy cryptologic detachment in Hawaii, opened in 1937, and CAST for the detachment first located at Cavite, then at Corregidor in the Philippines.

Intercepted messages were usually sent by courier or mail from Manila and Hawaii, but often there were delays in this service. Some intercepts were forwarded by teletype from the west coast of the United States. Even those forwarded electrically encountered processing delays for necessary logging, routing, filing, etc.

Laurance Safford, whom many consider the "founding father" of modern U.S. Navy cryptology, stressed the importance of High Frequency Direction Finding (HFDF), a source of intelligence at which, according to intercept, the Japanese were ahead of the U.S.

The Naval Research Laboratory developed equipment for the task, including the "Rotating Adcock" antenna, tested at Mare Island in 1933. In the late 1930s, the Navy began building up a network of direction finding stations in both the Atlantic and the Pacific regions. The first tracking of a foreign ship by a Navy D/F station in the interwar period occurred in 1936 from the Navy station in Cavite, Philippines.

By May 1940, OP-20-G had 65 HFDF operators at 16 stations. At that time, the Navy also operated 22 medium frequency Direction Finding stations, which it turned over to the Coast Guard so that OP-20-G could concentrate on HFDF.

Parenthetically, an unusual DF source was added to the Navy capability in the Pacific in 1940. Pan American Airways operated its own HF/DF network to support its air fleet, with stations at Wake Island, Midway, and Guam, among others. Pan Am agreed that these stations would cooperate with the Navy's DF stations on a time-available basis.

Direction Finding became one of the Navy's prime tools for locating the enemy just prior to and during the war.

One year to the day before the Japanese attack on Pearl Harbor, i.e., December 7, 1940, LCR Edwin Layton became the Intelligence Officer for the Pacific Fleet, based at Pearl; a few months later CDR Joseph Rochefort became Officer in Charge of the Navy's COMINT unit there. Layton and Rochefort had known each other as Language Officers in Tokyo, and their good working relationship would become an important factor in intelligence support to U.S. operations in the Pacific in World War II.

The Army began doing some intercept from overseas sites in the 1930s. In the early part of the decade, the Signal Corps established an intercept station at Fort Santiago in Manila. The primary purpose for this station was to copy Japanese press broadcasts for Military Intelligence. Secondarily, the station would copy Japanese military communications.

The Army also carried out intercept training for Japanese messages in "kana code" at the signal School at Fort Monmouth, New Jersey. As with the Navy's schooling, Army training was conducted by radio operators from detachments in the Far East who had taught themselves to intercept kana characters.

Although the Army intended to establish an intercept site for Japanese military traffic in Tientsin, China, in the late 1930s, a shortage of qualified intercept operators prevented this. A smaller station than originally envisioned was set up in Manila instead.

In mid 1940, Major Joseph Sherr was dispatched to the Philippines to improve intercept operations. More personnel were added to the intercept operations at the same time. The primary mission of the station, however, was Japanese diplomatic communications -- needed by SIS in Washington -- with military messages secondary.

Just prior to the outbreak of war, the Army had seven fixed intercept stations: Fort Hancock, N.J.; Presidio of San Francisco; Fort Sam Houston, Texas; Corazol, Panama Canal Zone; Fort Shafter, Hawaii; Fort McKinley, Philippines; and Fort Hunt, Virginia.

The Army did little cryptanalysis in the field. In 1939, the Signal Corps recalled its COMINT people from Hawaii and assigned them to Washington. Apparently the commanding general in Hawaii concurred -- he had no access to the Communications Intelligence produced, and their replacements could be put to more necessary -- from his point of view -- general signals duties.

The same attitude prevailed elsewhere. According to William Friedman, when the Signal Corps sent a small COMINT unit to Corregidor in the Philippines, it was only with great difficulty that the commanding general was persuaded to allow the personnel to do cryptanalysis. He needed them for general Signal Corps functions.



  • Doug Adams, "The Early Years," NCVA (Paducah, Ky.: Turner Publishing Company, 1996), pp. 9-10, 13.
  • Howard W. Brown, The Reminiscences of Lieutenant Colonel Howard W. Brown, Signal Security Agency, 4 August 1945, SHR-045, CCH Files.
  • Captain J. S. Holtwick, Jr., USN (Ret), Naval Security Group History to World War II, June 1971, SHR-355, CCH Files.
  • Carl A. Jensen, "The Story of the `On-The-Roof' Gang (OTRG)," NCVA (Paducah, Ky.: Turner Publishing Company, 1996), pp. 17-18.
  • James McIntire & R. D. Howell, Sr., "U.S. Marine Corps in COMINT," NCVA (Paducah, Ky.: Turner Publishing Company, 1996), pp. 46-50.
  • Frederick D. Parker, Pearl Harbor Revisited: United States Communications Intelligence, 1924-1941 (Center for Cryptologic History, 1994).
  • Anon., A Brief History of the Radio Security Station, FOURTH Marine Regiment, Shanghai, China, SRH-179, CCH Files.
  • Anon., A Brief History of the Radio Security Station Marine Detachment, Peiping, China, 15 April 1981, SRH-178, CCH Files.