This report was prepared as UNCLASSIFIED by Navy personnel with access to classified records and was reviewed by the Naval Security Group and later the NSA to ensure it contained no sensitive information. Archived at the NSG Repository in Crane, Indiana, Special Research Histories No. 186 (January 3, 1980) draws on various historical sources to provide a narrative of a naval activity. It is not an official Navy history, and its completeness and accuracy are not guaranteed.
Iwo Jima (Sulfur Island), a volcanic island in the North Pacific, was under Japanese control until 1945, when it became the scene of one of the fiercest and most costly battles in United States history, measured in terms of the ratio of casualties to the number of personnel engaged in battle. Iwo Jima is approximately five miles long and pork chop-shaped with the thick end, about two and one-half miles wide, toward the north. The island was strategically important since it was the best available air base between the Marianas, about 700 miles to the south, and Tokyo, about 700 miles to the northwest. In U.S. hands, it would provide an emergency landing field for B-29s and a base for fighter escorts for the bombers attacking Japan.
After 74 consecutive days of bombing by B-24s, the U. S. invasion force of 800 ships and 220,000 men arrived off Iwo Jima. D-Day for the invasion was 19 February 1945, when the first wave of Marines under the command of LT GEN Holland Smith, Commanding General, Expeditionary Troops composed of elements of the 3rd, 4th and 5th Marine Divisions totaling some 60,000 assault personnel, hit the beaches at 0859 to meet the 23,000 entrenched Japanese defenders under the command of LT GEN Kuribayshi.
The conquest of Iwo Jima had originally been scheduled for 14 days but, in fact, required 26 days with the island being officially declared secure at 1800, 16 March (D plus 26). However, fighting continued for some time afterward as remnants of the Japanese defending forces were flushed out of caves. In April and May 1945, some 1600 more Japanese defenders were killed on the island.
Establishment of a Naval Supplementary Radio Station (NAVSUPPRADSTA) was included in the development plans before the invasion and capture of Iwo Jima. The designation ‘WORKMAN” was assigned to the Iwo Jima movement and “URIK” was assigned as the shipping designator. The Fleet Radio Unit, Pacific (FRUPAC) News Memorandum for the week ending 5 December 1944, stated that LTJG Bobek would handle the installation of the direction finder at WORKMAN vice CRE Schmelzer.
On 30 December 1944, FRUPAC forwarded a memorandum to the Commander, Service Force (Advanced Base Section) outlining the requirements for the planned station on Iwo Jima. Initially, the station would consist of one Model DAW mobile D/F unit, one Model DP-15 D/F unit, and accessory radio receiving and transmitting equipment. With this configuration, the station would have an allowance of one officer and 16 enlisted personnel. The memorandum requested shipping space for 50 metric tons of material in the 4th Echelon and 25 metric tons in the 8th Echelon (see Appendix A).
On 19 January 1945, the Commander-in-Chief, U. S. Pacific Fleet and Pacific Ocean Area (CINCPAC/CINCPOA) forwarded a letter to the Island Commander, WORKMAN, directing the establishment of the NAVSUPPRADSTA. The station would be under the administrative command of the Commanding Officer, GROPAC ELEVEN, and would operate under the control of FRUPAC. The station would consist of direction finder units only and would operate as a station of the Mid-Pacific Strategic Direction Finder Net (see Appendix B).
The equipment for the 4th Echelon was loaded on board the SS NANCY HANKS at Iroquois Point, Pearl Harbor, on 27 and 28 February, and two men, RM2 Brubaker and RM3 Harkness, were assigned on board the ship to keep a check on the equipment and to be immediately available for unloading the Model DAW trailer and truck. On 4 March, twelve more enlisted personnel boarded the MS BOSCH FONTEIN at Pearl Harbor. The ship departed Pearl Harbor enroute to Iwo Jima the same day.
** Battle of Iwo Jima Feb 19, 1945 – Mar 26, 1945 **
On 16 March, FRUPAC informed the Officer-in-Charge, Naval Supplementary Radio Station, Navy #926 (Guam) that a direction finder station would be established on WORKMAN at approximately L plus 45 days. The station was to have one DAW D/F unit (1.5-22 mHz), one DAB-3 D/F unit (2-18 mHz), one DP-15 D/F unit (100-1500 kHz), one TBA-10 transmitter (1KW, 4-26 mHz), one TDO transmitter (400W, 2-18.1 mHz), one TCS transmitter (25W, 1.5-12 mHz), nine HF receivers, three generators, as well as miscellaneous testing and intra-station communication equipment, construction and maintenance material, spare parts, etc.
In the FRUPAC News Memorandum for the period 12-19 March 1945, it was reported that LTJG Bobek had departed for Iwo Jima (see Appendix C for personnel assigned to Iwo Jima).
On 28 March, LTJG Bobek forwarded a progress and information report on the establishment of Station “AN” (Iwo Jima). He departed Hawaii on 9 March and flew via Johnston Island and Kwajalein Island to Guam arriving there at 2330, 11 March. He reported to the Officer-in-Charge, Guam and briefed him on the proposed installation on Iwo Jima. LTJG Bobek departed Guam on 20 March at 0810 and arrived on Iwo Jima at 1230 where he reported to the Commanding Officer, Naval Affairs, Iwo Jima, and to the Commanding Officer, GROPAC ELEVEN. He observed that most of the personnel on Iwo Jima were living in foxholes and pup tents on temporary locations. Unloading of ships had been slow due to rough surf since it was necessary to use LST’s, LSM’s, and LCT’s and DUWK’s running up on the beaches during favorable weather because there were no breakwater or harbor facilities at the time. On 21 March, he toured the southern three-quarters of the island in company with a Navy and an Army Communications officer and visited the proposed site for the NAVSUPPRADSTA. On 22 March, LTJG Bobek called on LCOL Roberts, USA, the Island Signal Officer, and Col Morris, USA, the Island Engineer, to request that the station’s site be surveyed, staked out, and construction begun with the goal of completing the station seven days after the arrival of the 4th Echelon. The priority and sequence of construction was
- D/F control building ( 24’ x 24’ Quonset on concrete foundation)
- Power house on concrete foundation
- DAB D/F building (24’ x 24’ with concrete pit)
- DP-15 D/F building (8’ x 8’)
- Quonset hut (20’ x 72’) for quarters, mess hall, and galley,
The soil at the site was found to consist of coarse volcanic sand to a minimum depth of 12 feet. The D/F site was level and about 12 feet above sea level. It was considered that the site was the most suitable site on the island. The period 23-27 March was spent finalizing arrangements for the construction of the station and preparation of a formal Base Development Plan (BDP) to be followed. The 4th Echelon
was scheduled to arrive on 5 April and it was planned to give priority to bringing the DAW D/F unit ashore as soon as practicable on an LCT and attempt to have the unit operational the same day. LTJG Bobek also requested that RM1 C. A. Boyd and RM1 J. H. McArthur be transferred from Guam to Iwo Jima. These men had been transferred with him from Hawaii to Guam on 9 March where they were to remain until needed on Iwo Jima.
While earlier directives on Iwo Jima mentioned only, or at least initially, a direction finder mission for the station, a 2 April 1945, OP-20G memorandum established a requirement for 16 intercept operators to be transferred from Hawaii to Iwo Jima to man four intercept positions for research on low and medium frequency Japanese Naval circuits and for research on aircraft coverage not audible at Guam. The Japanese Naval positions would be controlled by FRUPAC and the aircraft positions by the Joint Radio Analysis Group, Forward Area (RAGFOR) on Guam. All intercept material would be forwarded by air to Guam from where it would be forwarded by teletype to FRUPAC. This was to be a temporary arrangement until a decision could be made whether Iwo Jima had any unique coverage possibilities over other stations then being planned.
On 12 April, LTJG Bobek forwarded another progress report. Construction plans had been reviewed with the 90th Naval Construction Battalion (NCB) of the 9th Naval Construction Brigade. Construction began on 1 April 1945. On 4 April, the station’s equipment, material, and 14 men arrived on board the MS BOSCH FONTEIN and the SS NANCY HANKS. On 6 April, RM1 Boyd and RM1 McArthur arrived from Guam by air bringing the station up to the original allowance of 16 enlisted personnel. The unloading of equipment and construction of the station continued. On 8 April, the 15KW Diesel generator was put into service. On 11 April, the DAW/ D/F unit was finally unloaded from the SS NANCY HANKS and put into operation. In an 110720Z message to Net Control, Pacific Strategic HFDF Net to Guam, LTJG Bobek reported that all receivers, the 25W TCS-9 transmitter, the DAW D/F unit, and generators were in operation. The station was operational with watches instituted at 0300Z. Construction of all buildings was complete. The watches established consisted of a three-man, three-section watch on the Pacific Strategic HFDF Net flash and reporting frequencies, the DAW D/F unit, and a search position.
At the time, the 90th NCB was still camped in the area of the station and station personnel were using the Battalion’s galley. Apparently the battalion was also providing security for the station since it was mentioned that, with the move of the 90th NCB, it would be necessary to request sentries for the area. This was not an idle request since LTJG Bobek reported that quite a few Japanese were still in the caves around the island. He reported that on 1 April, a group of 200 Japanese had made a Banzai attack close to the area of the station, which resulted in U. S. casualties of 7 dead and 70, wounded. Practically all of the attackers were killed but some did manage to escape back to their caves. He also reported that about 25 Japanese had recently been captured and brought into the POW camp located about one-quarter mile from the station.
On 12 April, LTJG Bobek learned of a 31 March Guam message requesting allocation of additional area for augmentation of the station, presumably in support of the impending VHF mission. On 13 April, installation of the Model DAB-3 and the DP-15 D/F units commenced. The DAW D/F unit was secured at 2100 local due to a warning of an impending Japanese attack. Japanese were encountered about 800 yards northeast of the DAW unit. Operations were resumed at 0700, 14 April. Also on 14 April, the station finally received the necessary cryptographic material to enable the station to fully participate in the HFDF net and the16 men ordered from Hawaii for research and intercept also arrived.
On 15 April, LTJG Bobek reported that the watches had been increased from three men to six men consisting of a D/F control operator, a DAW D/F operator, an HFDF search operator, and three research operators (one 4-8 mHz, one 15 kHz-4 mHz, and one 28-145 mHz). LTJG Bobek also reported that the 16 men who had reported from Guam for research and intercept duty were all inexperienced and would require on-the-job training. He apparently meant that they were inexperienced in operations
against Japanese targets since he stated that they had previously served in South American D/F Net and intercept assignments. The men had subsequently received 12 weeks of instruction and KANA training at Bainbridge Island, Washington, and had stood two strings of watches at Hawaii. He also mentioned that they had served together practically all of their time in service.
On 16 April, the installation of the Model DP-15 D/F unit was completed and it was put into operation on the 17th increasing each watch to seven men. On 18 April, it was reported that a temporary radial system was being installed for the Model DAB-3 D/F unit. A permanent radial system would be installed only after the mine disposal squad had inspected the area for mines and shell duds. Copies of research intercept logs were being forwarded to Guam and FRUPAC. With the arrival of RIP-5 typewriters from GUAM copies of intercepted traffic would also be forwarded to Guam.
On 20 April, the station was confronted with an unusual problem. About 18 100’ lengths of anchor chain were found to have been dropped in an area about 300’ west of the DAW D/F site the previous day and this mass of metal could adversely affect bearings. Through some effort on the part of LTJG Bobek and the Officer–in-Charge of the 90th NCB, the chain was soon moved from the area.
Work on the station continued and the seven-man, three-section watch schedule was maintained. On 22 April, the 90th NCB began moving from the area of the station and LTJG Bobek requested sentries from the Executive Officer of the Naval Base to provide the required security for the station. However, LTJG Bobek was told that he could have asked for nothing harder to supply at the time and no sentries were available for assignment to the station. As a result, it was necessary to assign the VHF search operator to sentry duty during the evening and mid-watches.
On 23 April, the installation of the DAB-3 D/F unit was completed and the equipment placed in operation replacing the DP-15 unit, which was placed in stand-by. With the activation of the DAB-3 D/F unit, a study of its and the DAW unit’s bearings was instituted with only DAB bearings being reported to the HFDF net for a time. Later, bearings on the same target from both units were reported to the net.
In the April 1945 Monthly Report, it was reported that the Naval Supplementary Radio Station, Iwo Jima, went into operation on 11 April and joined the Mid-Pacific Strategic HFDF Net on 15 April. The D/F Control and Intercept Building had been completed on 7 April, the DAB D/F Building and 20’ Quonset hut for quarters on 8 April, the Power House on 9 April, and the DP-15 D/F Building on 10 April. Six positions had been established as follows:
Position Mission Equipment
1 D/F Control 2 RBG-2 receivers
2 Intercept & Search 1 RBC-1 receiver
2 RBB-1 receivers
3 Intercept 2 RBG-2 receivers
4 Intercept 1 RBA-1 receiver
5 Intercept 1 RBA-1 receiver
6 (unmanned) 1 RBK-12 receiver
DAW D/F D/F net
DAB-3 D/F D/F net
Twenty-eight men were assigned to watch-standing duties with a seven man daily working party. One Chief Radioman was in charge of material and operations and two men were assigned to material and clerical work. One man was also hospitalized at the time of the report bringing the total of enlisted personnel assigned to 32. Communications with Guam for D/F and other operations utilized the Model TCS-9 transmitter, which was part of the DAW D/F unit. A Model TBA-10 transmitter, being installed in the Island Radio Transmitter Building, was expected to be in operation about 8 May. The Model DAW D/F unit had been brought ashore in an LSM on 11 April and put into operation two hours later. The DP-15 was installed and operational on 16 April and the DAB-3 on 19 April.
Fresh water for the station, as perhaps for the entire island, was rationed for drinking only and brackish water was hauled to the site for washing and bathing. An old Japanese well was located some 150 feet north of the living quarters. Approximately 24 feet deep with concrete casings some 50 inches in diameter, the first 12 feet of the well had been blown up by bombing and it would be necessary to remove the rubble and clean the well out to hopefully make it useful to the station. By 1 May
the well was cleaned out to the bottom and a pump had been installed. The pump was putting gout about 30 gallons per minute and the temperature of the water in the well was 170˚. The station salvaged two 100-gallon aircraft reserve fuel tanks for water storage for two showers, which were completed on 3 May (for pictures of the showers and other stations views, see appendix D). On 2 May, the station also received sentries for the station. Two were posted from sunset to midnight, and two from midnight to 0700.
Work continued making the station’s facilities more permanent. The 90th NCB brought in a ditch digger and dug trenches four feet deep to bury power and telephone cables between the various buildings of the station. One of the biggest questions at the time was when the equipment and material in the 8th Echelon, originally scheduled to arrive on D plus 75, or 5 May, was going to arrive. On 5 May, LTJG Bobek was told that the equipment was on the SS MOSES FARMER, which would be called up from Saipan in a week to ten days. On 9 May, he was again told a week to ten days. In the meantime, material laying around the area was put to good use at the station. In addition to the aircraft fuel tanks used for the showers, a 200 gallon aircraft fuel tank was installed as a fuel tank for the 15 KW Diesel generator and an electric pump salvaged from a B-29 was installed at the well.
As of 14 May, the station was still manning seven positions including the two D/F positions. The following material was being forwarded on a daily basis via officer messenger airmail:
- Intercepted traffic to Guam for teletype transmission to FRUPAC.
- Radio operator’s circuit logs for each ((Japanese)) circuit to FRUPAC and Guam.
- Report of Circuit receiving conditions for each ((Japanese)) radio circuit to FRUPAC and GUAM.
On 10 May, LTJG Bobek reported that a LCDR W. F. Harrington, USNR, had arrived and inspected the station. This was apparently just part of a general tour of the island because, based on LCDR Harrington’s 19 May report, it appears that his primary mission was to search for Japanese documents and equipment, specifically a cipher machine.
In his tour, he noted that there were many caves on the island to be investigated but he was primarily interested in locating the cave occupied by the Headquarters of the Japanese 109th Division. On 11 May, interrogation of Japanese prisoners identified two who had served on the Division Commander’s communications staff and would agree to lead investigators to the cave. The cave was located and the investigators were satisfied that it was, in fact, the Division Headquarters. However, everything had been destroyed by fire, either by the Japanese themselves or by U.S. forces using flamethrowers to clear the caves of Japanese. While many caves had been destroyed by engineers constructing roads, many remained and were still occupied by Japanese elements. An average of 20 Japanese prisoners had been taken daily for the past 30 days in clearing these caves. LCDR Harrington’s report closed with the statement that, “It is my opinion that the cipher machine, if on the island, is completely burned or buried and a pin point target will be needed to locate the machine.”
As of 19 May, the SS MOSES FARMER was still at Saipan with the station’s 8th Echelon equipment and there was no schedule as to when the ship would be called up to Iwo Jima to unload. In the interim, equipment was being borrowed from the Naval Base. On 20 May, the 90th NCB completed a 48 foot addition to the existing 20 foot Quonset hut section which permitted the movement of 18 men into more permanent living quarters but 12 men and the officers continued living in 16’ x 16’ pyramidal tents. The Quonset hut was borrowed because the station’s hut was in the 8th Echelon cargo. As of 21 May, the station was still manning four intercept positions, one D/F control position, and two D/F positions with one intercept position and the DP-15 D/F unit in standby.
In the Monthly Station Report for May 1945, LTJG Bobek reported that the SS MOSES FARMER finally arrived at Iwo Jima on 31 May with the station’s 8th Echelon equipment. The station had the following positions installed:
Position Mission Equipment
1 D/F Flash & Report 2 RBG receivers
2 HF Search & Intercept 2 RBB-1 receivers
Position Mission Equipment
3 Intercept 2 RBG-2 receivers
4 Intercept 2 RBB-1 receivers
5 Intercept 1 RAZ-1 receiver
1 RAK-6 receiver
6 Intercept 1 RBG-2 receiver
7 VHF Search 1 RBK-12 receiver
D/F D/F Net DAW-1 D/F unit
D/F D/F Net DAB-3 D/F unit
D/F D/F Net DP-15 D/F unit
It was reported that an eight-man, three-section watch schedule had been put into effect on 31 May indicating that one intercept and one D/F position remained unmanned. During the month, the DAW-1 D/F unit was moved to its permanent location completing the permanent installation of all of the D/F equipment. The installation of the TBA-10 transmitter in the Island Transmitting Room had been completed and the transmitter was functioning satisfactorily. The station had one 68’ Quonset hut of which 48 feet was being used as living quarters. The remaining 20 feet of the hut was being used as a transmitter room and work shop as well as living quarters for the RMC and the RM1 of the material force. The rest of the men were still living in four 16’ x 16’ pyramidal tents; four men to a tent. Officer berthing was a single 16’ x 16’ tent. Additional Quonset huts were promised in June. Personnel assigned to the station were eating in the Naval Base galley at Brown Beach. Water storage facilities had been improved with the installation of the two more salvaged aircraft fuel tanks. The station’s mailing address was listed as the U.S. Naval Supplementary Radio Station, Navy #3150.
On 2 July, LTJG Bobek reported that LT J. M. Walsh and ENS J. B. Hellon had reported on board for VHF duties on 23 June. Six Radiomen for the VHF unit had arrived on 26 June with two more still enroute. In addition to the VHF unit’s equipment supplied by ADNC (OP-20G) and FRUPAC, a Model SCR-555 and a Model SCR-556 VHF Direction Finder were supplied locally by the 1st Detachment, 8th Radio Squadron Mobile, U. S. Army. A Quonset hut, to be erected as the VHR Operations Building, was expected to be ready for the installation of the unit’s equipment by 10 July and it was projected that the unit would be in operation by 15 July. Logs, intercepted traffic, and recordings produced by officer messenger air mail to Guam, which would, in turn, F unit were to forward translations to OP-20G and FRUPAC.
In the June Monthly Station Report, it was reported that the station had maintained a nine-man, three-section watch through the month; the increase apparently brought about by the addition of a watch supervisor. Direction finder operations had been disrupted by the necessity of dismantling the DB-3 and the DP-15 D/F units due to predictions of a typhoon with force 10-11 winds and waves 20-30 feet high, which could have apparently swamped the areas where these two units were located. Fortunately, the storm did not reach the intensity predicted and no damage occurred to the sites thereby facilitating the rapid reinstallation of the D/F units. The station received five 20’ x 56’ Quonset huts during the month from the Naval Base of which one was to be used for the VHF hut. Of the remainder, three would provide additional berthing for officers and enlisted personnel and one would be used for office and storeroom space. A 20’ x 56’ Quonset hut, which arrived with the 8th Echelon material, would be used as a recreation hut.
In the Monthly Station Report for July 1945, it was reported that the station had maintained the nine-man, three-section watch schedule implemented in June. Seven intercept positions were installed as follows:
Position Mission Equipment
1 D/F Flash & Reporting 1 RAL-6 receiver
1 RBC-1 receiver
2 Search & Intercept 2 RBB-1 receivers
3 Intercept 2 RBG-2 receivers
4 Intercept 2 RBA-1 receivers
5 Intercept 1 RBA-1 receiver
1 RAK-6 receiver
6 Intercept 1 RBA-1 receiver
1 RBG-2 receiver
7 Intercept & Supvr 1 RBA-1 receiver
1 RBG-2 receiver
2 RBK-12 receivers
It was also reported that the number of sentries was reduced on 29 July from two to one on duty at a time indicating that security on the island was improving. Improvements to the station continued. Work was begun on the installation of a barbed wire fence around the station perimeter. On 7 July, a gasoline powered pump was installed at the well to replace the electric aircraft pump which had been salvaged from a B-29.
On 16 July, the SCR-555A VHF D/F unit was put into operation. By 28 July, the VHF Quonset had been erected and the VHF receivers and the Model DBB VHF D/F unit installed. By the end of the month, one 20’ x 48’ Quonsets had been constructed for the main office and storeroom and two 20’ x 48’ Quonsets were under construction for enlisted quarters.
On 4 August 1945, FRUPAC directed Station “AN” to discontinue operating the DAW D/F unit and to place the unit in temporary storage as it was planned to reassign the equipment to another station at some time in the future. The unit was secured at 121340Z August.
On 8 August, LT Walsh forwarded a message report on VHF intercept operations. The unit was averaging three recordings per day of VHF voice transmissions in the 27-38 mHz range using the RBK receiver and the recorder. The SCR-555 VHF D/F unit had proved too insensitive and unstable except on strong signals. The RDO receiver and the Model DBB VHF D/F unit had not proven useful to date due to their having a minimum range of 40 mHz. Lt. Walsh reported he was ready to leave Iwo Jima for Okinawa to make arrangements for a similar VHF installation there. On 21 August, FRUPAC responded and directed LT Walsh to remain on Iwo Jima pending a decision on the installation of the equipment on Okinawa. This delay was undoubtedly brought about the Japanese acceptance of surrender terms.
On 8 September, the Chief of Naval Operations (OP-20G) informed the Commandant, U. S. Coast Guard, that a number of Naval Supplementary HFDF Stations were no longer required for strategic HFDF use and could be made available to the Coast Guard. Iwo Jima was included in this list.
In the Monthly Station Report for August, it was reported that a nine-man three-section watch posture was maintained until 23 August at which time an eight-man, four-section watch was instituted reflecting the decrease of one intercept position. The station complement was reported as 41 men on board. Position configuration were listed as follows:
Position Mission Equipment
1 D/F Flash & Reporting 1 RAL-6 receiver
1 RBC-1 receiver
2 Search & Intercept 2 RBB-1 receivers
3 Intercept 2 RBG-2 receivers
4 Intercept 2 RBA-1 receivers
5 Intercept 1 RAK-6 receiver
1 RBA-1 receiver
6 Intercept 1 RBA-1 receiver
1 RBG-2 receiver
7 Intercept & Supvr. 1 RBA-1 receiver
2 RBG-12 receivers
VHF Search & Intercept 2 RDO receivers
1 RBK receiver
1 RBK-11 receiver
3 RBK-13 receivers
1 RBG-2 receiver
1 APR-1B
Intercepted messages were forwarded twice daily by officer messenger airmail with two copies to (text missing) for transmission to FRUPAC by teletype, one hard copy to OP-20GW and one hard copy to FRUPAC. Construction of the additional Quonset huts had been completed and living quarters consisted of three 48’ huts for enlisted personnel, one 48’ hut for officers and chiefs, and one 48’ hut for recreation. A new shower and washroom with a concrete deck had also been constructed.
On 20 September, FRUPAC reported the results of a conference with LT Bobek to OP-20G and recommended the following steps be taken toward decommissioning Station “AN”:
- In recognition of the present utility for air-sea rescue and surface operations, retain the Model DAB-3 and the Model DP-15 D/F units and associated equipment manned by one Chief Radioman and eight operators.
- Decommission the VHF and intercept facilities,
- Return all excess personnel and electronics equipment to FRUPAC.
OP-20G concurred with the recommendations and stated that the Iwo Jima station had been offered to the Coast Guard for operation as an air-sea rescue net but informal information was that the Coast Guard would be unable to accept the station.
In the Monthly Station Report for September, it was reported that a four-section watch of eight men per watch was maintained until 16 September at which time one intercept position was terminated reducing the size of the watch to seven men. On 25 September, orders were received to decommission the RO intercept and VHF intercept facilities. At 250600Z September, a two-man, four-section watch was put into effect consisting of a D/F control operator and a DAB-3 operator. The 27 men made available by this reduction in the station’s mission were transferred to FRUPAC by air during the period 28 through 30 September. On 16 September, LT W. Bobek had been relieved as Officer-in-Charge by ENS James B. Hellon. All electronic equipment released by the mission reduction was turned over to the Communications Officer, Naval Base, Iwo Jima, with the exception of the DAW D/F unit, which was overhauled and prepared for shipment to FRUPAC. A major event affecting the habitability of the station occurred during the month when the station obtained an electric washing machine from the 89th NCB.
On 1 October 1945, CINCPAC/CINCPOA concurred with the proposed decommissioning of several strategic HFDF stations, including Iwo Jima, which had been listed in a 31 August FRUPAC letter subject to CNO approval of a post-war plan which did not contemplate retention of the stations by the OP-20G organization. Retention of the stations for air-sea rescue purposes was also not envisioned since airways D/F facilities were being operated by the Army Airways Communications System of the Army Air Force in the same geographical area.
In the Monthly Station Report for October, it was reported that a two-man, four-section watch was maintained until 1200, 23 October, when the watch posture was modified to a one-man, four-section watch on the D/F control circuit, and a one-man, two-section watch on the DAB-3 D/F unit with the provision that the DAB operator could secure from 0000 to 0800 and sleep in the DAB hut subject to being awakened if required. The sentries who had been assigned to guard the station were withdrawn on 11 October as no longer necessary. Reference was made to searching on a special project assigned in a 17 October FRUPAC letter. Reports of results were to be forwarded to FRUPAC on a weekly basis but no other details were given.
On 16 November, FRUPAC informed OP-20G that the Coast Guard had decided to take over three of the strategic HFDF stations, which had been offered, to them but Iwo Jima was not one of the stations. OP-20G informed FRUPAC on 19 November that, at FRUPAC’s discretion and subject to CINCPAC approval, the station at Iwo Jima could be decommissioned. On 28 November, FRUPAC informed OP-20G that CINCPAC had approved Iwo Jima’s decommissioning.
On 29 December, the Radioman-in-Charge of Station “AN”, RMC J. W. Jones, USN, submitted the station’s decommissioning report. He reported that all equipment was secured at 060004Z in accordance with the COMNAVMARIANAS 050707Z DEC 45, which directed the immediate decommissioning of the station. All equipment was turned over to various activities on Iwo Jima. The majority of classified documents were destroyed with the remainder transferred to the RPSIO on Guam.
During naval Supplementary Radio Station Iwo Jima’s comparatively brief existence, a total of 23,474 sheets of Japanese traffic was intercepted during the period of 19 April through 31 August 1945. In addition, the station’s direction finder mission maintained the following bearing to flash percentages on Japanese units and friendly aircraft; April- 63%, May-76%, June-80%, July-85%, and August-79%.
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