.Q0 • V244e- ­ jelfter Ak211/63 ,t4,4AA' 4FIED REPORT on JAPANESE DEFENSIVE PLAN for the A8 ISLAND of SAIPAN 2iCH.111V '030Vt1932J SOUTHERN MARIANAS Prepared by • ENGINEER, EXPEDITIONARY TROOPS (TASK FORCE 56) JULY-1944 • ,•• DOWNG'IRDF I7 FAR t:•111:11, 111LS: keGT NJ, 714,";1'. DE:21.fi3SIfIED. DOD Diii 5200.10 ICIASSIFIED Litho by Map Repro Unit UPS Rocky Mount Aug 1944 4 Instructors ReaC.in.2,- this.Document (File No. Name Date 0121/336 REPORT on .. ,43N Ed; 4, -' r 11 tielV 1,4 ti t4 !,1 I ,• JAPANESE DEFENSIVE.PLAN t ii '',. i:4- #t 't :httt t-i for 1. ,) #, THE ISLAND OF SAIPAN 1,-....:, , ...... — 1. Source of Inform This report is 'ase' upon obser econnaissance of defensive positions and installations from 21 June 1944, to 16 July 1944, conducted by and under the supervision of the Engineer, Expeditionary Troops, Task Force 56;from the results of interrogation of prisoner of war, Major Kiyoshi Yoshida,former intelligence officer, Japanese 43d Infantry Division; and from information contained in captured document, Northern Marianas Group Operation Order A-4, dated 24 May 1944. Two small reconnaissance teams provided by Joint Intelligence Center, Pacific Ocean Area, each in charge of a junior officer, and attached one team each, to the Second and Fourth Marine Divisions, assisted materially in this work. 2. General Conception. A joint Japanese Army and Navy garrison was charged with the defense of SAIPAN. The primary mission of the naval force which on D-day numbered approximately 4000, was the installation and manning of coast defense weapons and the defense of the Navy Sector in which was situated the depot of naval and coast defense stores. Orders prescribed that in the event of attack the command of coast defense batteries in Army Sectors would at once pass to the commanders of these respective sectors. The Army combat troops were estimated at 20,000 on D-day and were disposed in three sectors: Northern, Central and Southern. These three sectors and the Navy Sector are shown on attached map ANNEX A, based upon information taken from map attached to captured operation order. The failure of the Japanese garrison to successfully defend SAIPAN, while primarily attributable to the skillful leadership, and to the fighting qualities of our troops, was in a great measure due to the rapid pace of our thrust through the Gilbert and Marshall Groups, our bypassing of the Truk Group, and our unexpectedly early appearance in the Marianas. Every coastal defensive and antiaircraft battery position visited gave evidence of intensive activity in preparation for attack; not a single battery position or fortification was inspected in which the construction or installation was entirely complete. In many instances, casemates, emplacements, and magazines were less than half finished. In one case, a well-sited antiaircraft battery with well-built reinforced concrete emplacements lacked its weapons; in another, a battery of three (3) 140mm guns was found loaded on railway cars nearby GARAPAN NAVAL BASE, and another of three (3) 120mm dual purpose guns with the weapons in cosmoline lay on the ground nearby the partially excavated gun positions. In the GARA DEPOT were found the following items of ordnance. DOWNQRADIED AT 12 YEAR Nor AUTOMATICALLY DECLAS6IfIED: • 3 - 5 inch coast defense guns DOD DIE 5200.10 1- 140mm coast defense gun,(tube and carriage). 32- 120mm dual purpose guns,(tubes and carriages). 6 - 200mm mortars, complete. There can be little doubt that a large proportion, if not all of these weapons, were destined to be installed on SAIPAN. The effectiveness of our submarine.warfare, had doubtless contributed much to the delay in the shipment of construction material so vitally needed for fortification work. ••• The defense of the island evidently was premised upon the denial to landing forces of all beaches on the east and south shores, to the use of TANAPAG HARBOR, and to a dependence upon a mobile Army force to defeat enemy troops landed elsewhere. This assumption is supported by the location of permanent coast defense and dual purpose weapons, reinforced concrete blockhouses, and by the actions of the Japanese garrison once our troops had landed on Beaches RED, GREEN, BLUE and YELLOW. The enemy had placed great reliance upon his field artillery arm,- and once our drive had deprived him of the great bulk of these weapons, the dominant factor which delayed our attack was the advance over excessively rugged and difficult terrain. Likewise, this topography greatly favored the guerrilla tactics of the badly disorganized enemy forces. In spite of evidence of accelerated preparation of coast defenses, the Army garrison appeared neither well organized nor equipped. In this small theater so suitable for the employment of field artillery, the Japanese had neither horses nor mechanical prime movers designed to provide the mobility for this arm. Evidently the only means of movement were by rear drive trucks designed for use on roads, or by manpower. Both of these means obviously failed, as the bulk of field artillery was abandoned as the enemy withdrew northward. In his rapid withdrawal to the mountain fastness of the high mass extending northward from Hill 500, and dominated by MT. TAPOTCHAU,the Japanese forfeited any opportunity for maneuver. Thus, 0121/336 L' REPORT ON JAPANESE DEFENSIVE PLAN FOR-11 with artillery lost and a purely defensive role dictated he had no organized defensive positions to which to retire - only the precipitious terrain studded with cliffs and caves, and cut by numerous deep canyons generally crossing the direction of his retirement. Insofar as training in defensive warfare is concerned the Japanese Army forces displayed a lack of knowledge thereof almost astounding for modern troops. There was practically no evidence of organization of the ground; the principal airfield was practically undefended against ground troops, and on the night of D-day the enemy was unable to stage a counter-attack of sufficient strength to seriously affect our ultimate success. The lack of employment of beach obstacles and land mines were amazing. No mine fields of any consequence were found on any of the beaches used, and those found inland as the attack progressed were small, feeble, and relatively ineffectual. While two types of mines new to this force were encountered no large stocks were found. His initial employment of field artillery is worthy of note. On the first high ground and on the reverse slope thereof, three thousand (3000) yards southeast of Beaches GREEN and BLUE were massed sixteen (16) 105mm howitzers, and thirty (30) 75mm field pieces. Three thousand (3000) yards directly east of Beaah GREEN TWO was emplaced one (1)150mm howitzer battery of four (4) weapons, and three thousand (3000) yards directly east of Beach GREEN THREE was a like battery of four (4) howitzers. These weapons were particularly well sited and undoubtedly were responsible for much of the prolonged fire on the landing beaches. It is estimated that one battery alone had fired more than one thousand (1000) rounds. As previously pointed out, as our forces drove the bulk of the enemy northward, he abandoned most of his artillery, although he was able to continue to support his infantry by mortar fire. The only observed instance of field artillery emplaced on the shore was one (1) battery of four (4) 75mm light mountain guns in position practically on the beach one thousand (1000) yards southwest of the southern limits of CHARAN-KANOA, sited for fire on the channel through the reef just west of CHARAN-KANOA. This was one of the few known attempts of the enemy to make a stand at the beach. It is believed that this battery was silenced prior to D-day. On map of SAIPAN, ANNEX B, are shown beaches, and locations of massed enemy artillery. 3. Coast Defense Weapons and Beach Defenses. (1) Beginning at AGINGAN POINT at the most westerly extremity of the island and proceeding in a counter clockwise direction a description of coast defense weapons and beach defenses follows with photographs and sketches of the various installations.• Page numbers at end of each lettered subparagraphs are those on which photographs and/or drawings of installations described may be found. On overlay to Map of SAIPAN, ANNEX C, are shown the approximate locations of installations described, and, Map of SAIPAN, ANNEX B, with grid system may be used to further locate these with reference to terrain features. (a) One (1) battery of two (2)6 inch British, Whitworth Armstrong guns, Model 1900, located on AGINGAN POINT,(coordinates 03.4-14.5).. There was no indication that either of these guns had been fired. Tubes of both guns had been damaged by naval gunfire or aerial bombardment. Construction at this installation was incomplete. One gun was sited in completed reinforced concrete casemate. The walls and overhead cover in second casemate had not yet been poured. The fire control and range finder equipment for this battery were destroyed. Casemates limited the traverse of weapons to approximately 900 west to south. The ammunition storage facilities at the battery were very limited, although approximately one hundred (100) rounds were found in a cave six hundred (600) yards to the southeast. One gun was sited for fire on the channel between SAIPAN and TINIAN, and the other on the approaches to beaches RED; GREEN,BLUE and YELLOW.(See page 12). (b) A reinforced concrete blockhouse generally rectangular in shape, 28 ft. by 26 ft. provided with one (1) gun compartment and embrasure, was found four hundred (400) yards southeast of AGINGAN POINT,(coordinates 03.7-14.3). This small fortification suitable for a 20mm On was well sited for fire on Beach WHITE ONE.