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Corregidor: 
The Beginnings

Primary source: SRH-l80 Pre-World War II Radio Intelligence Activities in the Philippine Islands

The island of Corregidor is one of five islands guarding the entrance to Manila Bay. Running from north to south are La Monja, Corregidor (Fort Mills), Caballo (Fort Hughes), El Fraile (Fort Drum) and Carabao (Fort Frank).

CORREGIDOR ISLAND MAP

Corregidor,  the  largest of the islands,  some 1735 acres in total,  lies two  miles  from  the  southern  tip  of Bataan Peninsula and  seven miles  from Cavite Province, dividing the mouth of  Manila Bay  into what was called  the North Channel and the South Channel.

Corregidor is shaped like a tadpole with the head facing the South China Sea and the tail curling back into Manila Bay. Topographically, the island is divided into five parts. The high, round head of the island rising to 628 feet in elevation forms an area about a mile in diameter which was nicknamed "Topside"  and was the site of all the heavy batteries, the post headquarters,  a nine-hole golf course,  a huge enlisted barracks, a parade ground, and most of the living quarters. Moving eastward toward the tail of the island, the ground slopes downward about 100 feet to a plateau nicknamed "Middleside" where the hospital,  post  stockade,  service  buildings,  warehouses,  more barracks,  and quarters were located. On the north, or Bataan side of "Middleside" was a ravine called Power Plant Ravine which contained the island's electrical generation plant. From "Middleside," the ground slopes steeply downward another 300 feet  or so to "Bottomside" which is the lowest part of the island occupying an area about 300 yards from beach to beach and about 200 yards wide. Located here were more warehouses and various post utilities as well as the small village of San Jose, where most of the island's workers lived. Two docks, one on each side of the island, permitted small ships to unload supplies. Separating "Bottomside"  from the eastern part of the  island  is Malinta Hill,  some 390 feet high,  through which Malinta Tunnel was dug.  Passage around Malinta Hill was  possible via two narrow roads, carved from the slopes of the hill which were called the North and South Shore Roads. The remainder of Corregidor is the long, twisted tail of the island, about two and one-half miles long, which was given no particular name.

CUSTOM MAP

The move of Station "C" to Corregidor represented the conclusion of several years of plans, negotiations, and construction. The original idea of moving  the  Radio  Intelligence Station,  as  it was  then called,  was  apparently first conceived by CINCAF, Admiral Upham,  and the Asiatic Communications Intelligence Officer, LT J.N. Wenger, in 1933.

About 29 May 1934, a proposal was informally presented to the Army which requested  authorization  to  establish  a  radio  direction  finder  station  on Caballo Island.  On 15 June 1935 the Army replied that no immediate action was necessary since it appeared the Navy Direction Finder Station was functioning well  at the Cavite site.  In actual fact, disapproval by the Army was due to the fact that they were due to undertake a plan to install a DIF on Caballo, and the Army did not want intermingling of Army and Navy personnel..."as the Army contends that it is conducive to lowering the morale of the Army troops owing to differences in pay." Negotiations continued.

Several years later, the Secretary of War informed the Secretary of the Navy that  the Commanding General,  Philippine Department had been authorized to begin work on the construction  of the tunnel for the radio intercept sta­tion. By 31 Auqust 1939, the following projects were identified: Project AFIRM, the Radio Intelligence Tunnel; BAKER, the Direction Finder Site, and CAST, the quarters of personnel of Station "C".

In  early  October  1939,  Project AFIRM was given the official  title of “Navy Emergency Radio Station,” and the cover story that it was to "provide standby (communications capability) for Cavite and conduct research (in) long distance reception with experimental equipment". A  model  DY  Direction  Finder was to be installed, a Model DT-l  Direction Finder was to be calibrated  and placed in storage on Corregidor and a Model OP IFOF (Intermediate Frequency) was scheduled to be installed and the Pan American Airways' variously located 0/F's were to be calibrated to assist the District Radio Security and Inshore Tracking Organizations in time of emergency

Finally,  on  14 October  (Z)  Station  "C"  began to move to Tunnel AFIRM. Station  "B"  Guam,  was to establish watches to insure maximum coverage until the new "C" was operational, which occurred on 17 October 1939.  The station reported that  noise  level  permitted coverage of frequencies not copyable at Cavite.  Coverage,  staff,  and  equipment  was  increased  when  Station  "A"  at Shanghai was closed on 10 December 1940, and coverage of the Japanese Consular net was assumed.

References suggest two units had been established at Station "C", a general unit," assumed to be the intercept space,  and a "special unit," assumed to be the crypto unit, which included a Purple Machine, to decipher Japanese Diplomatic traffic.  The  "special"  unit  also used various IBM (International Business  Machines)  equipment  including  an  alphabetical  tabulator,  a  card sorter, a punch,  and a reproducing gang punch. Attempts were made to have ENS Ralph E. Cook,  at Cavite Navy Yard,  assigned to the Station "C" complex, but this was  not accomplished until  after Cavite was destroyed by bombing on 10 December.  This IBM equipment was dismantled and readied for shipment to Aus­tralia when the evacuation of Station "C" personnel began,  and IBM in Manila had  instructions  to destroy the equipment if Manila fell; but the equipment was not destroyed.  It was taken to Tokyo. (Even though a Tokyo IBM person was removed from prison camp to work on the installation,  it was later reported the Japanese never used the equipment.)

On 8 January 1942, COMSIXTEEN reported to OPNAV that all  radio intelli­gence publications had been destroyed except the RIP 5 typewriters and several communication ciphers. The Purple Machine was readied for evacuation, copies of intercept material were not being filed. A message from COMINCH (Commander-in-Chief, Pacific) to CINCAF of 31 January 1942, read in part:                  

SINCE THE WITHDRAWAL OF SINGAPORE CI UNIT TO COLOMBO, COM­MUNICATIONS  INTELLIGENCE ORGANIZATION UNDER YOUR COMMAND IS OF SUCH IMPORTANCE TO SUCCESSFUL PROSECUTION OF WAR IN FAR EAST THAT SPECIAL EFFORT SHOULD BE MADE TO PRESERVE CONTINUITY.  SUGGEST  CONSIDERATION  OF  PARTIAL  EVACUATION FORT MILLS UNIT 10 ESTABLISH NEW CI UNIT AT .  .  . OR AUSTRALIAN BASE       

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