Appendix C

Highlights from COM-14 Daily COMINT Summary

This appendix represents abstracts taken from the daily COMINT summaries published by COM-14. To aid the reader in correlating these highlights with actual daily events, I have included salient extracts from Morison's History of U.S. Naval Operations. To show the correlation between COMINT and warnings issued by Washington, I have also inserted, at the appropriate times, diplomatic and OPNAV messages.

The sources are indicated as follows:

"S" indicates COM-14 Traffic Intelligence Summaries, July-December 1941, SRMN-012.

"C" indicates Radio Intelligence publication Number 87Z, The Role of Radio Intelligence in the American-Japanese Naval War, Volume I, by Ensign John V. Connorton, USNR (SRH-012).

"M" indicates Volume III, The Rising Sun in the Pacific, 1931-April 1942, by Samuel Eliot Morison.

Edited copies of the COM-14 Daily Summaries for the period 1 November-6 December 1941 may also be found in PHA, Part 17, 2601-42.

S 16 Jul Combined Air Force concentration in Takao [Taiwan] included in 3rdFlt addresses. Indications it will move south, i.e., to Taiwan from Japan. 4thFlt concentrating in Mandates [Defense?)] Hiryu and probably other carriers concentrating in Taiwan area "awaiting the assumed Southern Operations."
S 31 Jul New Task Force Formed -- CINC3, China Flt, South China Flt.
S 20 Aug AirRon4 move indicated by heavy traffic.
S 21 Aug Commander AirRon24 at Saipan.
S 24 Aug New carrier, Shokaku -- appeared in traffic. [Confirmed by COM-16 no 28th.]
M Sep Training by carriers and air groups for Pearl Harbor attack began in September.
S 8 Sep New carriers Shokaku and Zuikaku being fitted out. [The Shokaku completed fitting out on 8 August 1941, the Zuikaku on 25 September 1941.] Plane complements for all carriers are being completed.

-71-


page 72

S 12 Sep COM-16 [confirmed] a new force being organized, possibly a 5thFlt.
S 18 Sep Heavy air-related traffic suggests air movement into Mandates forthcoming.
S 22 Sep Ashigara relieved by Isuzu as Flag of South China Flt. [Isuzu is Flag of DesRon5/3rdFlt.]
S 23 Sep Task Force being formed out of elements of 1st/2ndFlts.
S 24 Sep Additional carrier division organizing. [The Shokaku and Zuikaku later became CarDiv5.]
S 26 Sep Preparations noted for large-scale 1st/2ndFlt exercises with carrier divisions.
S 28 Sep Preparations may indicate possible hostile action.
S 1 Oct 2ndBasFor [3rdFlt] to board ship [possibly Flagship 3rdFlt] at Sasebo leaving some units behind.
S 2 Oct COM-14 says, "3rdFlt being built up to its French Indochina composition."
S 4 Oct Volume of traffic since callsign change indicates reorganization. COM-16 agrees that flag of CINC Combined Flt shifted to Mutsu [BatDiv1/1stFlt] and Flag CINC2 is in Maya (CruDiv4, 2nd section, 5thFlt).
M 5 Oct Carrier air groups officers told Pearl Harbor their objective. Training continued.
S 9 Oct Yokohama Air Corps addressed message to Taiwan addressee. Chitose Air and AirRon24 to move to Mandates soon. Naval Auxiliaries in Mandates continue to increase, now 33.
S 11 Oct Chitose Air moving to Saipan without commander. Yokohama Air at Truk as is commander AirRon24. Large air unit appears at Hainan and Kanoya. Large air movements noted in 4thFlt.
S 12 Oct Commander Yokohama air at Kwajalein.
S 14 Oct Movements to Mandates noted by Yokohama, Chitose, and Yokosuka Air units.
S 15 Oct 5thFlt is formed.

-72-


page 73

S 16 Oct Communications network is expanding particularly in air-related communications. Callsign usage same as for "Temporary Shore" or "Advanced Base" stations associated with South China, Indochina campaigns.
S 16 Oct CINC Combined Fleet may have returned to Nagato. Associated with 1st/2ndFlts, carriers, and subs. Chitose Air en route Mandates, Yokohama Air at Truk, Yokosuka Air possibly Palau area. Evidence that Navy is taking over Maru vessels and issuing callbooks and organizing into units.
S 17 Oct Tokyo relayed message from Spratly Island [South China Sea] to Takao [Taiwan] under priority procedure to COS Combined Flt, ComCarDiv4, CarDiv4, Intel unit Bako (Taiwan), COS South China Flt, COS French Indochina Force (Southern Exped. Force), Resident Naval Officer (RNO) Taihoku [Taipei], Cdr 11th Air Corps [sic] [Fleet], and COS South China Air Force. [COM-14 confused over whereabouts of CINC Combined and status of Mutsu as Flagship.] During last week September Mutsu joined 2nd Flt after stint at yard at Kure. On 1 Oct, CINC2 "relieved as CINC Combined and hoisted flag on Mutsu." On 17 October, CINC2 retransmitted message originated on 14th addressed as follows: Action: 2ndFltColl, 3rdFltColl, Combined AF, SubRon5, SubRon6, AirRon7, BatDvi3; Info: ComCarDivs, CINC Combined, Radio Takao, Radio Palao, Radio Tokyo. A total of 38 Naval Auxiliaries in Mandates.
S 18 Oct CINCChinaFlt replaced; date unknown. Appears to be heavy air movement between Empire and Mandates.
S 19 Oct Guam reports 13 new Naval Auxiliaries in Mandates. [Hawaii and Philippines disagree over callsign for a new carrier -- either Zuikaku or Shokaku.]
S 21 Oct Japanese DF traffic first noted on 20 October is increasing. Stations at Chinkai, Manchukuo area, Chosen area, Jaluit, Sasebo. Combined Air Force sent message which included carriers in addresses. COM-14 notes this not normal and that scope of addees indicates a large-scale operation over a long distance. Action: Navy Minister, Chief Naval General Staff (NGS), Combined Air Force, CarDiv4 less HOSHO and U/I, CarDiv3; Info: CINC China Flt, CINC South China Flt, all major Fleet Flagships.
S 22 Oct 11 Maru vessels noted using suffix denoting "C.O. Naval Detachment Aboard" in connection with Takao/Hainan air movement. A 5thFlt continues to appear. The "Special Task Force" or "Southern Expeditionary Force" [SEF] [Flag in Kashii] associated with CarDiv4 in future operations. Impression grows that a large-scale operation is in progress in Mandates, in Takao/Hainan/Indochina areas and in Kuriles.

-73-


page 74

S 23 Oct COM-14 noted message from DF Hq Tokyo to collective addressee which omitted CINC South China Force but included SEF, "a circumstance reminiscent of Indochina operations when 3rdFlt assumed major importance with CINC South China Force in subordinate role."
S 24 Oct 2ndFlt sent message to unusual action addressees not normally under 2ndFlt and information addressees which give southern flavor to whole group. Action: 3rdFltColl, CombinedAirColl, 2ndFltColl, BatDiv3, DesRon3; Info: Palao; Spratly/Cam Ranh; DF; Tokyo; CINC Combined; ComCarDiv5.
S 24 Oct Communications Officer CarDivs message to following addressees: BatDiv3, CruDiv8, CarDivs less CarDiv3; Info: Tokyo Radio, U/I addressee, Communications Officer Combined Flt. [Major units of Pearl Harbor Strike Force. See Appendix A, same date, for related messages.]
S 26 Oct U/I Air Command to move from Taiwan to South China. 5thFlt becoming more tangible at Yokosuka.
S 28 Oct COS French Indochina Force aboard Flagship Combined Fleet. Indications growing that 4thFlt is preparing for operations. CINC4 sending traffic to Combined Flt, Subs, CarDivs, and Tokyo addressees.
S 30 Oct Tokyo ComDiv message volume unprecedented. Possible communications change in offing COM-14 believes movement of 3rdFlt imminent. Station C reports Ashigara departed for South. New carrier [Koryu] associated with Saipan, Truk, and Yokosuka Air suggesting move to Saipan soon.
S 31 Oct Japanese Navy callsigns changed in Fleet and Air units. Commanders 11 and 12 Air Corps [sic], Shiogama Air in Takao area. COM-14 noted similarity to concentration at Hankow Air, July-August.
S 1 Nov All major fleet callsigns recovered. Shore callsigns no change. Individual callsigns slow to collect and recover.
S 3 Nov General messages continued to emanate from Tokyo in unprecedented numbers. Numbers not understood now that communications change past. COM-14 suggested that messages were reports of some kind. A new addressee reading 1stAirFlt noted for first time. This is a new organization. Possibly explains association between CarDivs 3 and 4 and Combined AF, i.e. between shore-based and Fleet Air. [See Appendix A, 4 October and 6 October, for earlier appearances of 1stAirFlt address.]
S 6 Nov Tokyo radio now using "general" or "area" calls vice unit calls and may have eliminated address and originator from messages on broadcast circuits. Very heavy air concentration on Taiwan includes the entire Combined Air Force Commander and Staff, one carrier division, and the Fleet Air Arm.

-74-


page 75

S 7 Nov Possible heavy concentrations in Marshalls causing congestion on Mandates circuits.
S 8 Nov Formation of Force in Takao/Bako area [Taiwan] under Cdr Combined Air nearly completed based on reports addressed to CINC Combined Flt; Naval Ministry; CdrCarDivs; Combined Air; 1stFlt and Shore addressees associated with movement or organizational changes. Force possibly includes CarDivs3 and 4 plus Auxiliaries, and units of Combined Air and 1st Flt. Uncertain area of operations.
C 8 Nov Details of U.S. aircraft in Philippines sent to Tokyo by Manila on 1 November.
S 9 Nov COS SEF in Tokyo.
M 10 Nov Japanese Army and Navy agree to attack plan. Pearl Harbor Strike Force departs home waters for Kuriles. [See Appendix A.]
S 10 Nov Combined Flt mostly in Kure area, BatDiv3, CINC2, and two CruDivs noted specifically. 3rdFlt in Sasebo/Takao; 4thFlt in Truk; 5thFlt has one unit at Chichi Jima; CdrCarDiv3 possibly with Combined Flt units at Kure/Sasebo; CINC Combined AF at Takao.
C 12 Nov Messages from Tokyo to Manila on 5 November request information regarding aircraft and ships.
S 12 Nov CarDiv3 returned to Kure from Takao per COM-16.
S 13 Nov Activity of BatDiv3 unclear -- Flag at sea, Cdr in Yokosuka, DivComOfficer active with Truk, Saipan, Palao -- other ships in Div unlocated. One CruDiv of 2ndFlt in traffic with Palao, possibly in that area. Other units of 1stFlt seem inactive. Carriers inactive.
S 14 Nov 4thFlt Staff members in Tokyo. Carriers remain in home waters with most in port. Flag of BatDiv3 heard. DesRon3 and CruDiv7 of 2ndFlt active, may proceed south.
S 15 Nov Combined Fleet to BatDiv3, DesRons1/3, associated with SEF. CINC2 most active -- appears to be arranging operations of units involving 1st/2ndFlts, carrier and air units. Purpose of air concentrated in Takao area unknown; possibly will move south to SEF.
S 16 Nov 1st/2ndFlt units remain in Kure area. CINC2 has assumed an important role involving units of several fleets, SEF, Combined Air, CarDivs and Mandates fleet. DesRon1 is operating with CarDivs and BatDiv3.
C 18 Nov OPNAV sent messages to CINCAF regarding Japanese patrols from Mandates and Dutch concerns/intentions regarding Japanese buildup in Mandates which also threatens Netherlands East Indies.

-75-


page 76

S 18 Nov CINC Combined Flt active sending and receiving messages. CINC2/SEF/Combined AF association very plain in messages sent and received. BatDiv3, CarDivs, two DesRons associated in traffic. CINC2 in command of large Task Force comprising 3rd Fleet, Combined AF, some CarDivs, and BatDiv3. No movement from home waters has been noted. 3rdFlt will move from Sasebo in near future. 2ndBasFor may be transporting air units or equipment.
S 20/21 Nov Unusually heavy traffic Tokyo to all Majcoms. NGS urgent precedence to COS South China Flt. Personnel Bureau sending long personnel messages. DF traffic heavy. Tokyo/Takao circuit forced into duplex to handle traffic. Combined Fleet: Flags of 1st/2ndFlts in Kure area. Most of both Flts in Kure;/Sasebo area. BatDiv3 still in Yokosuka area. Traffic to and from CINC2 abnormally high; association with CINC3 continues. Partial list of forces being assembled by CINC2 in two days (27 units, 11 Marus) includes CarDiv3, AirRons6/7; CruDivs5/7; DesRons3/4/5; BasFor1/2; Shiogama Air Corps; possibly two additional air units; and 13 U/I units. Mandates/4thFlt: Palao seen as locale for forthcoming concentration of forces based on communications activity. Concentration in Marshalls far greater than Palao.
M 22 Nov Pearl Harbor Strike Force completes move to Kuriles.
S 23 Nov High precedence traffic increasing. Typical headings are (a) from Tokyo Address to Collective Shore; Info: COS Combined, 1st/2nd/3rd/4th/5thFlts, SEF; (b) from COS3 to COS2; Info: COS Combined F, SEF; (c) from Tokyo to COS3 and SEF; Info: Sama, Hainan; (d) from U/I Flt unit to Radio Takao and Hainan, U/I/ Flagship; Info: Radio Tokyo and 2ndFlt Flagship; and (3) from Iwakuni Air to Iwakuni Air Detachment at Naha, Takao; Info: Kure, Bako and U/I unit Takao. Indications are that 3rdFlt units are under way in a movement southward coordinated with 2ndFlt, Combined AF, and SEF.
S 24 Nov Increased activity among 3rdFlt addressees with a high percentage of movement reports. Large number of messages associate CarDiv3 with CINC3. No definite location for carriers.
C 24 Nov OPNAV message warning of possible Japanese "aggressive movement .. in any direction." Mentions Philippines and Guam as possible objectives.
S 25 Nov High level of traffic suggests that organizational arrangements or other preparations are not yet complete. Genzan Air Corps has been in Saigon for eight days, according to callsign analysis. Other units of Combined Air Force possibly moved to French Indochina area from Taiwan. One or more CarDivs in Marshalls now.
S 26 Nov CruDiv7 of Combined Fleet received traffic via Sama indicating arrival in Hainan waters, probably accompanied by DesRon3. Takao, former Flagship 2ndFlt active in association with 2nd/3rdFlts. No movement of

-76-


page 77

    Flags newly formed force noted as yet. CINC5 association with new Task Force.
C 26 Nov COM-14 260110Nov41 to OPNAV, Info: CINCPAC, CINCAF, COM-16; "JAPANESE NAVY ORGANIZATION OF FLEETS Submitted by the 14th Naval District Communication Intelligence Unit: Since the latter part of October, the Commander-in-Chief of the Second Fleet has been forming a Task Force consisting of Second Fleet, Third Fleet (including First and Second Base Forces, and First Defense Division), Destroyer Squadron Three, Submarine Squadron Five, Combined Air Force Air Squadron Seven. Possibly vessels of the Third Battleship Division in the First Fleet. Third Fleet units are believed to be moving in the direction of Takao and Bako. It appears that the Seventh Cruiser Division and the Third Destroyer Squadron are an advance unit and may be en route to South China. The Combined Air Force has assembled in Takao, and indications are that some of it has already moved to Hainan Island. It seems that the Second Base Force is transporting equipment of the Air Force to Taiwan. Radio calls for the South China Fleet, the French Indochina Force, and the naval stations at Sama, Bako, and Takao appear also in heading of dispatches concerning this task force. The Resident Naval Officer, Palao, and the Third Base Force at Palao have communicated extensively with the Commander-in-Chief of the Third Fleet. It is thought that a strong force of submarines and air groups are in the vicinity of the Marshall Islands. This force includes the 24th Air Squadron, at least one aircraft carrier, and probably one third of the submarine fleet. The 14th Naval District Communications Intelligence Unit evaluates the foregoing information to indicate that a strong force may be preparing to operate in Southeastern Asia while component parts of the Task Force may operate from the Marshalls and Palao."
M 26 Nov Pearl Harbor Strike Force departs Kuriles.
C 27 Nov COM-16 261331Nov41, to CINCPAC, COM-14, OPNAV, CINCAF; "JAPANESE NAVY-ORGANIZATION OF FLEETS Date of Issue-27 November 1941. Following has been submitted by the 16th Naval District Communications Intelligence Unit, referring to and commenting on yesterdays' information from the 14th Naval District Communications Unit. During the past few days traffic analysis indicates that the Commander-in-Chief, Second Fleet, is directing units of the First, Second, and Third Fleets, and Submarine Force organization that apparently will be divided into two sections. For purposes of clarity the units expected to operate in South China will be referred to as First Section and units expected to operate in the Mandates will be referred to as Second Section. The estimated units in First Section are Cruiser Division Seven, Air Squadron Six, Defense Division One, Destroyer Squadron Three, and Submarine Squadron Six. The Second Section consists of Cruiser Division Five, Carrier Division Three, (Ryujo and one Maru), Destroyer Squadrons Two and Four, Submarine Squadron Five, Base Force at Palao, Fifth Base Force at Saipan, and lesser units unidentified. Cruiser Division Six and Battleship Division Three may be

-77-


page 78

    included in First and Second Sections respectively, but status cannot be clarified yet. There are slight indications today that Destroyer Squadron Three, Cruiser Division Seven, and Submarine Squadron Six are in the Takao area. The balance of Third Fleet units in doubt but may be assumed that these vessels including Destroyer Squadron Five will take stations in the Straits of Formosa or further south. Combined Air Force units from the Empire proper are in Paidoh. [Possibly Paiho in South Central Taiwan.] It is impossible to confirm the supposition of reference report that carriers and submarines are in the Mandates. The best indications are that all known First and Second Fleet carriers are still in Sasebo-Kure area. Directives to the above Task Forces, if such, are directed to individual units and not to complete groups. Special calls usually precede formation of Task Force used in area operations. Commanders-in-Chief, Second, Third, and Southern Expeditionary Fleet, appear to have major roles. Traffic from the Minister of the Navy and the Chief of Naval General Staff to Commanders-in-Chief of the Fleet appears normal. This evaluation is considered reliable."
S 27 Nov Some tactical traffic from carriers intercepted. DF activity high. No evidence of movement Combined Fleet from Kure-Sasebo area. Carriers still located in home waters.
C 27 Nov OPNAV WAR WARNING message alerts all Pacific commands to "An aggressive move ... within the next few days." Possible objectives mentioned: Philippines, Kra Peninsula, Thailand, or Borneo. Guam and Samoa to take measures against sabotage.
C 28 Nov Naval attaché, Shanghai, on 25 November sights troop transports heading southwest; on 26 November, sights warships led by cruiser, possibly Naka [2ndFlt] heading south. Also reports that between 19 and 26 November, he had sighted many transports, many loaded with troops, headed southwest.
S 28 Nov Communications volume between South China, Mandates, and Empire very heavy. No tactical traffic seen. Suspected "RI" net very active and becoming more so. DF and RI nets operating at full strength upon U.S. naval communications and getting results. In the Combined Fleet, no indications of any movement any Fleet units. In 3rdFlt, 1stBasFor possibly not in Sasebo but en route somewhere. In 4thFlt area, 4thBasFor at Truk, Yokohama Air Corps at Ruotto, and Wotje in communications with AirRon24 and Kamoi.
C 29 Nov OPNAV WAR WARNING message. Text indicates Army also received warning. (290110Nov41)
C 29 Nov COM-16 reports CINC2 to move south between 29 November and 2 December. [291029Nov41]

-78-


page 79

S 29 Nov Traffic volume above normal. Traffic to South China very high. Intelligence-related messages numerous, e.g., 11 from Tokyo to Majcoms. Tokyo Radio Intelligence sent four long messages to Majcoms. DF net very active. Existence of 11thAirFlt confirmed. Not a Navy element. Arrival of AirRon7 in Takao confirmed. Following units under immediate command of CINC2: CarDiv3, DesRon2, SubRon5, DesRon4, SubRon6, 3rdFlt, CruDiv5, SEF, CruDiv7, and possibly two battleships subordinate to 3rdFlt.
C 30 Nov OPNAV directs CINCAF to reconnoiter line from Manila to Cam Ranh Bay for evidence of Japanese preparations to attack Kra Peninsula.
S 30 Nov Traffic volume low; old messages being repeated. AKAGI (CV) heard on tactical circuit. Naval General Staff sent one urgent precedence message to COS Combined, 2nd/3rd/4th/5thFlts; Combined AF; Subs and China Fleets. in the Combined Fleet, COS, Combined and 1stFlts in Kure, COS2 is unlocated, possibly at sea. CINC2 addresses message to Kongo (BB) and Hiyei (BB) which places them in his Task Force. CINC3 possibly underway. 4thFlt area: CdrSubs headed for Marshalls. Evidence points to sub concentration [COM-16 disagrees]. Presence of AirRon24 and Yokohama Air suggests future Air/Sub operation from Marshalls. Presence of plane guard DDs suggests at least one carrier in Mandates.
C 1 Dec COM-16 reports ships from 3rdFlt arriving Formosa. Notes CINC2 in Flagship Atago has moved south.
S 1 Dec All radio calls of units afloat changed at midnight. Unusual. Service calls usually last six months. Suggests an additional progressive step in preparing for active operations on a large scale. 1stFlt: nothing to indicate Fleet out of home waters. Believe most of 1stFlt is in 2ndFlt Task Force. 2ndFlt believed proceeding from Kure/Sasebo in direction of South China, Indochina, probably passing up Takao. CruDiv7 and DesRon3 definitely in Indochina area. 3rd/4th/5thFlts NTR, Carriers, NTR; Combined Air Force, NTR. Large numbers of subs believed east of Yokosuka/Chichi Jima and Saipan.
S 2 Dec COM-14/COM-16 disagree on precise location of 2nd/3rdFlt Task Force. COM-16 places in Takao area in communications with Takao radio. COM-14 did not hear but did note Takao sending traffic to Tokyo for these fleets suggesting they are not near Takao. Both seem to agree that the large fleet has left Empire waters. COM-16 reports nine subs vicinity Cam Ranh Bay, possibly SubRons5/6 which have been included in 2ndFlt Task Force. Possible that Combined Fleet staff has split, part to 2nd/3rdFlts, part elsewhere. 2ndFlt believed under way in company. 3rdFlt NTR. Carriers, almost complete blank. Traffic at low ebb. Not one callsign recovered. Some units of Combined AF have left Takao area.

-79-


page 80

C 3 Dec OPNAV reports Japanese diplomats burning codes.
S 3 Dec 2nd/3rdFlts probably under way. Subs and carriers, NTR.
C 4 Dec OPNAV orders certain U.S. intercept sites to burn codes.
M 4 Dec Malay invasion force departs Hainan.
S 4 Dec Tokyo sends large number [12] of urgent precedence messages to Majcoms. Intelligence sent seven-part message to COS China Flt, Combined Fleet, 3rdFlt, South China Flt, SEF, and Sama. CINC2 and CINC3 very quiet but receiving much traffic. CINC2 in vicinity of Takao. Cinc Combined sent messages to U/I; Info: 3rdBasFor, Palao, CINC2, and CINC3.
S 5 Dec All circuits overloaded. Tokyo-Mandates circuit duplex. Many new schedules. Both Takao and Tokyo handling traffic for 2nd/3rd Flts, some of which is old traffic. A plaintext message from a ship's captain from Tokyo to Takao referring to the Far Eastern crisis, notes that "specific orders will be issued soon." No traffic from Cdr carriers to sub force seen. In the 3rdFlt, a "COS" sent a message to "Commander 14th Army" aboard Ryujo Maru in 3rdFlt. A number of Maru vessels have been addressing CINC3. Shiogama Air and 2 U/I Corps are moving to probably Indochina.
C 5 Dec Diplomatic message from Manila to Tokyo on 28 November details U.S. air patrols.
C 6 Dec Diplomatic message from Honolulu to Tokyo on 18 November details ship movements in Pearl Harbor.
S 6 Dec Traffic volume heavy but much old traffic seen. Much confusion in routing/delivery. Four stations now holding broadcasts: Tokyo [3] , Saipan, Ominato, and Takao. CINC4 in Truk area, never in Jaluit. Definite close association between 3rdBasFor, Palao and forces in South China, e.g., 2nd, 3rdFlts, SEF, and Bako. Arrangements largely neglected by CINC4. 5thFlt dispersed in Empire waters.

Table of Contents
Appendix B *   Notes on Sources



Table of Contents Image of anchorNotes on SourcesImage of anchor Abbreviations