EFENSE INSTALLATIO ON IWO JIMA I Classification ch*ng*d to ED Maj., Inf. Custodian CINCPAC-GINCPOA BULLETIN NQ. 136-45 10 JUNE 1945 8 JUN1945 Defense Installations on I WO JIMA flaintly CINCPAC-CINCPOA FLEET MARINE FORCE V AMPHIBIOUS CORPS 3rd, 4th & 5th MARINE DIVISIONS JICPOA L" 50607- 23 THRU 144 UNITED STATES PACIFIC FLEET AND PACIFIC OCEAN AREAS MCH/cc HEADQUARTERS OF THE COMMANDER IN CHIEF 10 June 1945 - Serial DIS-1OO93O From: Commander in Chief, U. S. Pacific Fleet and Pacific Ocean Areas. To: Distribution List. Subject: CINCPAC-CINCPOA BULLETIN No. 136-45. Defense Installations on Iwo Jima. Enclosure: (A) Subject bulletin. 1. Enclosure (A)., forwarded herewith,. need not be reporte_ d and when no longer of value should be destroyed. No report of destruction is necessary. M. LBpENDRE, By direction. Copies ARMY 5 ComGenAAASch Ft Bliss Tex 5 SIORAAFComAldAFSWPA APO 923 2 CO AMS War Dept 1 DistCom APO 960 5 Chief of. Engrs War Dept 1 DistCom APO 961 5 Chief of Ord War Dept 1 DistCom APO 962 2 Chief Sig Off War Dept 2 The-EngrUSAFPOA APO 958 5 ComdtCASch Ft Monroe Va 25 ComGen APO 7 2 ComdtCom&GenStaffSch 25 ComGen APO 27 Ft Leavenworth Kan 25 ComGen APO 77 12 ComGenAAF War Dept 25 ComGen APO 81 2 DirJointTargetGroup AAF 25 ComGen APO 96 Pentagon Bldg Wash DC 25 ComGen APO 98 12 ComGenAGF War Dept 15 CO 4thAimdGrp APO 957 2 ComGen2ndAF Colorado Springs Colo 10 ComGenTEN APO 357 2 ComGen4thAF SF Calif 10 ComGenTAFTEN APO 357 2 ComGenWesDefCom Presidio SF Calif 5 ComGenWPBC APO 244 2 CO AeroChartServAAF War Dept 3 ComGenAGF APO 86 . 2 CO OrdBDCAberdeenProvingGround 3 ComGenAGF APO 244 Aberdeen Md 3 ComGenAGF APO 245 2 ComGenAAFSATAAFTAC Orlando Fla 3 ComGenAGF APO 246 14 MISReadingPanel War Dept 3 ComGenAGF APO 247 2 OPD War Dept 3 ComGenAGF APO 331 1 ChiefPACMIRS Camp Ritchie Md 3 ComGenAGF APO 457 1 CO AimyUnitWestCoast PO Box 651 3 ComGenAGF APO 458 Tracy Calif 5 ComGenCPBC APO 956 3 ComGenSEAC APO 432 NY 10 ComGenCombatTrCom APO 957 3 BGS(I)MainHqALFSEA APO 432 NY 10 ComGenlCorps APO 301 1 CO CPICAirComSEA New. Delhi India 10 ComGenlXCorps APO 309 2 ComEasternAirComSEA APO 671 NY 10 ComGenXCorps APO 310 2 DMIGHQ New Delhi India 10 ComGenXlCorps APO 471 2 ComGenUSAF APO 885 NY 10 ComGenXIVCorps APO 453 1 ComAirComSEA New Delhi India 10 ComGenXXIVCorps APO 235 1 SuptSEATIC APO 885 NY 10 ComGenXXIVCorpsArty APO 235 14 ComGenUSAFCTO APO 879 NY 5 ComGen2273HAAAC APO 958 2 ComGenl4thAF APO 627 NY 5 C02274HSAC APO 956 2 OinCSINTIC APO 879 NY 5 ComGenSPBC APO 502 2 ComGenllthAF APO 980 Seattle Wash 1 CO 45thCABn APO 264 4 ComGenAdvCPAlaskan Dept APO 980 2 ea ArmyIsCom Seattle Wash 5 CinCAFPac APO 500 2 ComGenNZAHq Wellington NZ 5 CoordinatorATIS APO 500 15 ComGenPOA APO 958 5 OinCCOICGHQSWPA APO 500 2 CO 30thEngrBaseTopoBn APO 957 5 ComAldAF APO 923 2 CO 64thEngrBaseTopoBn APO 246 2 CO AldGeogSecSWPA APO 923 200 ComGenAAFPOA APO 953 10 ComGenFEAF APO 925 20 COEGHQSWPA APO 500 2 ComGenl4thAAComRearEch APO 322 10 ComGenUSAFFE APO 501 2 ComGenl4thAAComFwdEch APO 500 10 ComGenUSASOS APO 707 10 ComAdvAldLandHq APO 925 2 DirNEFIS APO 500 2 CO FwdEchCenBuGHtlSWPA APO 500 2 DirADVANEFIS APO 926 25 ComGenSlX APO 442 50 CinCGHQSWPA APO 500 25 ComGenElGHT APO 343 12 ComGenASF War Dept 10 June 1945 Serial DIS-1OO93O OinCPICNYd Wash 2 AcornU'raDet Pt Hueneme Calif CO NavResLab Belief 2 BuAer/ OinCTAIC NAS Anacostia DC 2 BuOrd ComAirPac 3 CNAOpTra Jacksonville Fla 2 ComNorPac 2 AC/AS (I) AirMinA13USA 2 ComSoPac Whitehall Via CNO 2 MEIU#1 FPO SF 5 AirMinistry London Via CNO 2 MEIU#4 FPO SF 2 DMI MI 2 Whitehall Via CNO 1 ComBatRonTWO 2 ail MI 15 London Via CNO 1 ComBatDivTWO 2 DNIAdmty Whitehall Via CNO 2 ea ComBatDiv 25 CNO 1 ea CO BB 1 USNLOOSS Via CNO 2 ComCruDesPao 2 ComdtANSCol Wash DC 1 ea ComCruDiv 2 Comll 1 ea CO CA CB CL 2 Coml2 1 ea ComTaskFlot 2 Coml3 1 ea ComDesRon 2 Coml7 1 ea ComDesDiv 2 ComUSNB PtHueneme Calif 1 ea ComCortDiv 2 ComdtNavV/arCol Newport RI 1 ea CO DD 65 ComAiriant 1 ea CO DE PF 2 ComPhibTraPacFPO San Diego Calif 3 Com3rdFleet 1 ComFair Seattle 5 Wash, 3 Com5thFleet 3 CominCh 3 Com7thFleet 2 ComOpTraPac San Diego Calif 1 Coml4 1 ComServLant. 1 DIO 14ND 1 ComSubLant 45 CO SEFIC 2 CO NavalUnitWestCoast 5 OinCAlCCinCPOAAdvHq 3 CO NACIS NAS quonset Pt RI 1 OinCAlCNorPac 2 ComUSNavGrp Navy 169 NT 100 OinCJDU Navy 943 5 ComPhibsPac 100 OinCJDU Navy 3011 150 AdComPhibsPac 1 AtCom Navy 3233 2 OinCRearEchComPhibsPac 1 ea NavylsCom o/o AdComPhibsPao 1 ea CO NavAdvBase 10 Com3rdPhibFor c/o AdComPhibsPac 1 ea ComNavBase 10 Com5thPhibFor 1 CO NAS Seattle Wash 10 Com7thPhibFor 1 ComdtNOB Navy 3256 5 ea ComPhibGrp 1 ea ComNOB 2 ComSubPac ' 4 AdCominPac 2 ComSubPacSubordCom 2 ea ComMTBRonPac 3 DNINavy Dept Melbourne Australia 2 ComMTBRonsSWPA 3 SNORNethNavyinAustralia 441 St Kilda 2 ea ComSeaFronPac Rd Melbourne Australia 2 ComServPac 2 ComMarianas 1 ea ComServRonPac 2 ComNavy 3233 2 DirAdBaseComServPac 2 ComNavForces Navy 3256 5 CO InterpRonONE Navy 3256 2 ComSubArea Navy 3254 5 CO InterpRonTWO FPO SF 2 RepComDesPacCentPacFwd MARINE CORPS ComGenFMFPao 25 ea ComGenMarDiv Comd tMarCorps 5 ComGenTraComFMF LeJeune ComGenlllPhibCorps 5 ComGenTraComFMF Pendleton ComOenVPhibCorps 5 DirofAviationMarCorps ComGenMarCorpsSchooIs 2 ea karlsGom BRITISH 3 COIS BPF 2 Captain EscortForcee 3 COIS EIS 1 ea SenOffMinFlot 1 RAdmCom4thCruRon 1 ea CO BB 1 RAdmComDDs 1 ea CO CL 1 RAdmComFltTrain 1 ea CO DD 1 ea ComDesFlot 1 ea CO DE 1 ea CO FltTrainShip Table of Contents JAPANESE DEFENSIVE PLAN AT IWO JIMA . 2-6 ILLUSTRATIONS . 7-119 General Terrain Features 7-16 Beaches ......... 7-10 Terrain Inland * , 11-16 Obstacles and Mines 17-20 Mines 17-18 Trip Wire 19 Anti-Tank Ditches • 20 Caves 21-25 Coast Defense - Artillery 26-39 15 cm CD Guns 26-26 14 cm CD Guns 29-31 12 cm CD Guns 32-33 12 cm (Short) Naval Guns 34-37 8 cm CD Guns 38-39 Antiaircraft and Dual Purpose Batteries 39-64 12 cm DP Guns 39-42 10 cm DP Guns 43-45 7 cm AA Guns 46-48 25 mm AA MG 49-58 13 mm MG 59-60 Searchlights ........ 61-64 Blockhouses 65-70 Covered Artillery Emplacements 71-86 120 mm Howitzers 71-74 75 mm (Type 38) Field Guns 75-78 75 mm (Type 90) Field Guns • 78-80 47 mm Ant i-Tank Guns 8I-85 37 mm Anti-Tank Guns 86 Open Artillery Emplacements 87-88 47 mm Anti-Tank Guns 87 37 am Anti-Tank Guns 88 Mortars 89-95 320 mm Spigot Mortars . ­ 89 150 mm Mortars 90-92 81 mm Mortars 93-94 Grenade Launchers . 95 Rockets 96-IOO 200 mm Rocket Launcher 96-98 250 kg Rocket Launcher 99 63 kg Rocket Launcher 100 Pillboxes 101-103 Rifle Pits 104-105 Tanks 106-108 Dummies 109-111 Radar and Radio Station 112 Revetted Vehicles 113 Air Raid Shelters ....... 114-115 Ammunition Storage '. 116-117 Miscellaneous ... .... 118-119 MAP APPENDIX Enemy Defense Installations as observed from ground study. Arcs of Fire for Casemated Coastal Defense Guns on Iwo Jima. Anti-Aircraft Defenses. Blockhouses with principal directions of fire indicated. Covered Artillery with principal directions of fire indicated. Japanese Defensive Plan At Iwo Jima The strategic importance of IWO JIMA. need hardly be emphasized. Its value as an airbase midway between the MARIANAS and the heart of JAPAN has already been proved. After the occupation of SAIPAN, the Japs must have known that IWO would be attacked* The only question was VHEH. The story of their haste in constructing defenses is told in aerial photographs from 15 June 1944 until D-Day, 19 February 1945. INCREASE OF FORTIFICATIONS At the time SAIPAN was invaded, only AA defenses, hasty fire trenches, and pre­ liminary beach defenses had been prepared at IWO JIMA, By September 1944* positions had been constructed in depth behind the beaches. Company and platoon positions were then in evidence, and concrete pillboxes and covered artillery emplacements were under construction. By December, most beach positions were completed and had been strengthened by the construction of heavy concrete blockhouses. A cross-island defense line in depth protecting the northern part of the island was springing up along the high ground north of Airfield No. 1. Additional AA defenses, increased numbers of covered artillery and coast defense guns, and more and more concrete positions and minefields on the beaches were noted on each succeeding photographio softie. By D-Day, key positions had been connected with pillboxes and were protected by covering fire from artillery, anti-tank guns, and mortars, previously sighted in. Intelligence prior to the invasion of IWO indicated a formidable garrison force with many major caliber weapons and extensive tank and personnel obstacles; however, aerial photographs and maps gave only a limited picture of one of the enemy*s best defensive weapons, the terrain. An amphibious assault in force was limited to the east and west beaches of the narrow southern part of the island. These conditions gave the Japs an advantage in preparing defensive positions for all-around security. Only small groups were needed to cover very narrow beaches with steep exits along the northern coast. COVER AND DISPERSAL , Captured documents, confirmed by ground study, indicate the enemy's battle strength was conserved by countermeasures against shelling and bombing. The terrain was well suited for cover, and caves were so numerous in some sections of the island that it was impossible to plot them all on a 1:10,000 map.