Satchel Charge

JAPANESE WEAPONS

 

When the Americans invaded Okinawa, the total strength of the 32d Army amounted to more than 100,000 men, including the 20,000 Boeitai draftees and an unknown number of conscripted Okinawans. The army proper totaled 77,000, consisting of 39,000 Japanese troops in infantry combat units and 38,000 in special troops, artillery, and service units. (For the troop list of the 32d Army, see Appendix B.)

Weapons of the 32d Army

The armament of the Japanese on Okinawa was characterized by a high proportion of artillery, mortar, antiaircraft, and automatic weapons in relation to infantry strength. Their supply of automatic weapons and mortars was generally in excess of authorized allotments; much of this excess resulted from the distribution of an accumulation of such weapons intended for shipment to the Philippines and elsewhere but prevented by the shortage of shipping and the course of war from leaving the island. The Japanese also had an abundant supply of ammunition, mines, hand grenades, and satchel charges.{157}

On Okinawa the Japanese possessed artillery in greater quantity, size, and variety than had been available to them in any previous Pacific campaign. Utilizing naval coastal guns, they were able to concentrate a total of 287 guns and howitzers of 70-mm. or larger caliber for the defense of the island. Of this total, sixty-nine pieces could be classified as medium artillery, including fifty-two 150-mm. howitzers and twelve 150-mm- guns. The smaller pieces included 170 guns and howitzers of calibers of 70- and 75-mm. In addition, seventy-two 75-mm. antiaircraft guns and fifty-four 20-mm. machine cannon were available for use in ground missions.

The principal mortar strength of the 32d Army was represented by ninety-six 81-mm. mortars of the two light mortar battalions. The Japanese also possessed, in greater numbers than had previously been encountered, the large 320-mm. mortars, commonly called spigot mortars; the 1st Artillery Mortar Regiment, reputed to be the only one of its kind in the Japanese Army, was armed with twenty-four of these. Standard equipment of the ground combat units of the army included about 1,100 50-mm, grenade dischargers (knee mortars).

To counter American tank strength, the Japanese relied, among other things, on an unusually large number of antitank guns, especially the 47-mm. type. The independent antitank units had a total of fifty-two 47-mm. antitank guns, while twenty-seven 37-mm. antitank guns were distributed among the other units of the Army. The entire Japanese tank force, however, consisted of only fourteen medium and thirteen light tanks, the heaviest weapon of which was the 57-mm. gun mounted on the medium tanks.

The 32d Army relied heavily on a great number of automatic weapons, well emplaced and plentifully supplied with ammunition. Its units possessed a total of 333 heavy and 1,208 light machine guns. In the course of the battle many more were taken from tanks being used as pillboxes and from wrecked airplanes. The 62d Division alone wielded nearly half the automatic weapons of the 32d Army and was by far its most potent unit.

The Japanese Plan of Defense

The active formulation of a defense plan for the Ryukyus dates from the American capture of the Marianas in June and July 1944. The first plan for the ground defense of the Ryukyus was established in a 32d Army directive of 19 July 1944. This document outlined a plan to destroy the Americans at the water's edge; that failing, to "annihilate" them from previously constructed positions, embodying a fortified defense in depth. In accordance with this directive, construction of cave and underground positions began in the summer of 1944. The command on Okinawa was convinced that the situation was urgent and informed the troops that "the Empire is determined to fight a show-down battle with an all-out effort for the preservation of national unity when the enemy advances to the Nansei Shoto."{158} In instructions issued in August 32d Army Headquarters stated:

The enemy counteroffensive has become increasingly severe and they have infiltrated into our central Pacific defense area and are now boldly aiming toward the Nansei Shoto. Should we be unable to defend the Nansei Shoto, the mainland and the southern frontier would become isolated. Thus, the execution of the present war would be extremely difficult and would become a life-and-death problem for our nation.{159}

In the early part of 1945 important changes were made in the original defense plan. It was decided not to attempt the destruction of the invading forces at the beaches, but to have the 32d Army offer a strong resistance around a central fortified position; a decisive land battle would be avoided until the Kamikaze planes and the Japanese fleet should destroy the American warships and transports. The general character of the final plan reflected the critical situation that faced General Ushijima with the departure of the 9th Division for Formosa and with the fading of prospects for reinforcements. He had to alter his plans to fit his resources, so depleted by now that he had to mobilize virtually the entire civilian population of the island.

 

Map No. 9: Japanese Defensive Positions

 

The Japanese high command was determined to hold Okinawa and planned to employ the major portion of the Empire's remaining air strength as well as a large portion of its fleet in an attack on the American sea forces. The Japanese hoped to isolate and weaken the invading ground forces by destroying the American naval units and support shipping lying off Okinawa. To accomplish this, they relied chiefly on bomb-laden planes guided to their targets by suicide pilots, members of the Japanese Navy's Special Attack Corps known as the Kamikaze (Divine Wind) Corps. This desperate measure was expected to equalize the uneven ground battle by cutting off the Americans from supplies and reinforcements. It would enable the 32d Army to drive the invaders into the sea.

Despite the hopes of the Japanese high command, planning of the 32d Army for the defense of Okinawa proceeded on the assumption that it was impossible to defeat the enemy and that the most that could be done was to deny him the use of the island for as long a period as possible and inflict the maximum number of casualties.{160} Acting on this assumption, General Ushijima drew his forces together into the southern part of Okinawa and, from the strongly fortified positions around Shuri, prepared to make his stand there as costly to the enemy as possible. He would not go out to meet the invaders; he would wait for them to come to him, and force them to fight on his own terms. The 32d Army artillery was instructed not to fire on the invading ships and landing forces, in order to avoid revealing its positions and exposing them to the devastating naval gunfire of the Americans. Units were not to oppose landings in their sectors until enough enemy troops had been brought ashore to render escape by sea impossible. The 32d Army planned to defend only the southern third of Okinawa strongly. The principal defenses would be established in the rugged ground north of Naha, Shuri, and Yonabaru. Landings north of this line would not be opposed; south of it the Americans would be met on the beaches.

Wherever the Americans landed, they would eventually come up against the Shuri defenses, where the main battle would be fought.{161}

The Japanese estimate of American plans was very accurate. The enemy expected the Americans to land across the Hagushi beaches on the west coast, with from six to ten divisions, and to strike out for the Yontan and Kadena airfields. He anticipated that American landing forces would form large beachheads of 2-division strength each, hold within these perimeters until sufficient supplies were unloaded to permit a strong attack, and then advance behind massed tanks and concentrated artillery fire. The Japanese estimated that it would take the Americans about ten days to launch their attack against the main Shuri defenses. They believed that the Americans intended to draw the main Japanese force into the Shuri lines so that a not too costly secondary landing could be effected with perhaps one division on the east coast somewhere south of Shuri, near Minatoga.{162}

The 32d Army disposed its available troops in accordance with its general plan of defense and its estimate of the enemy's capabilities. Only two battalions of the 2d Infantry Unit were left in the north to defend not only the Motobu Peninsula but also Ie Shima, where they destroyed the island's airfield.{163} The only force stationed in the area immediately behind the Hagushi beaches was the 1st Specially Established Regiment, Boeitai, which was ordered to fight a delaying action and then, after destroying the two airfields in the sector, to retreat.{164} The 62d Division manned the defensive belt across the island north of the Naha Shuri-Yonabaru line. Its 63d Brigade was to absorb the shock of the American attack southward at the narrow waist of the island between Chatan and Toguchi, while the main line of resistance was established from Uchitomari to Tsuwa north of the Shuri defenses. Deployed to support the 63d, the 64th Brigade was dug in to fight in the successive positions around Shuri. Artillery attached to the 62d Division was emplaced in direct support on the west side of the line.{165} (See Map No. 9.)

Having selected the Shuri area as their main battle position, the Japanese with shrewdness and great industry organized the ground for a strong defense. The main zone of defense was planned as a series of concentric positions adapted to the contours of the area. Caves, emplacements, blockhouses, and pillboxes were built into the hills and escarpments, connected by elaborate underground tunnels and skillfully camouflaged; many of the burial tombs were fortified. The Japanese took full advantage of the terrain to organize defensive areas and strong points that were mutually supporting, and they fortified the reverse as well as the forward slopes of hills. Artillery and mortars were emplaced in the caves and thoroughly integrated into the general scheme of defensive fires.{166}

To meet the threat of landings in the south, the 32d Army stationed the 24th Division in defensive positions covering the Minatoga beaches and extending across the southern end of the island.{167} The 44th Independent Mixed Brigade was moved to the Chinen Peninsula and was ordered to cooperate with the 24th Division in repelling any landings in the area. Artillery was registered on the Minatoga beaches, and some of the 320-mm. mortars were moved to this sector.{168}

During the long period of planning the Imperial General Staff and the 32d Army were constantly concerned with fixing the probable date of the American invasion; each changed its view several times and on occasion they were not in agreement. It was during and after the invasion of Saipan, Tinian, and Guam, in the summer of 1944, that the Japanese first expected an immediate invasion of Okinawa and, accordingly, began to pour troops into the island. But after the invasion of the Palaus and Leyte in September and October 1944 the Imperial General Staff in Tokyo considered it unlikely that sufficient American troops would be immediately available for another major operation.{169} During the Philippines operations at the end of 1944 the Imperial General Staff in Tokyo was in doubt as to whether the next blow would fall on the south China coast or on Formosa,{170} although the command of the 32d Army was still convinced that Okinawa would be invaded and pushed forward preparations for its defense.{171}

Again, at the beginning of 1945 the Imperial General Staff was uncertain whether the next American attack would be against Formosa or Okinawa. By the end of February, as a result of the invasion of Iwo Jima, which pointed to the American strategy of cutting off the Japanese home islands from the mainland and the Indies, the Japanese concluded that Formosa would be bypassed and that Okinawa would be the next target.{172} Their aerial reconnaissance and intelligence reports revealed an increase in west-bound American shipping to the Philippines and the Marianas during the latter part of February—an increase that swelled to large proportions early in March; this seemed a clear indication of the imminence of another American operation.{173} When the invasion fleet appeared off Iwo Jima, it was considered by some to be a feint for the invasion of Okinawa.{174} With the Iwo Jima battle in progress and submarine activity increasing around the Ryukyus, it was taken for granted that the invasion of Okinawa would soon follow, on or about 1 April 1945.{175}

As one of the last steps in preparing for the expected struggle, the Japanese command on Okinawa on 21 March ordered all air, shipping, and rear-echelon units to "prepare for ground combat." On 27 March, the day after the American invasion of the Keramas, 32d Army advised its units that "the enemy is planning to land his main strength tomorrow, the 28th, on the western coast of southern Okinawa, in particular in the Yontan-Kadena sector."{176} When the American forces invaded Okinawa, a few days later than had been predicted, the 32d Army adhered strictly to its plan of offering little resistance until the invaders should come up against their outposts at the Shuri line. The Japanese Combined Fleet Commander, meanwhile, prepared to execute his plan, delayed by Task Force 58's foray into the Inland Sea in March, to destroy the American fleet by air and surface action. Before many days had passed, the enemy was to react to the invasion with a fury never before encountered.

Enemy Counterattacks by Air and Sea

The American command was aware of the likelihood of formidable attacks by both air and sea on the assault forces. Okinawa was close to the Japanese homeland, where the remaining strength of the enemy's naval and air forces was concentrated. To meet the expected air offensive from the nearby fields of Kyushu. Shanghai, and Formosa, the Americans relied upon Task Force 58, the Tenth Army's Tactical Air Force, the guns of the fleet and supply ships, the British task force, and land-based antiaircraft artillery. To ensure early warning of Japanese raids, the Navy established around Okinawa a ring of picket stations, manned by destroyers and destroyer-type vessels, to which gunboats (LCS) and later LSM(R) types were added to give increased fire power. These stations were all less than 100 miles from Zampa Point, the peninsula just north of the Marine beaches; some, were only a few miles off the coasts of the island. Combat air patrols were maintained day and night over the picket stations, which could also call for aid from the routine combat air patrol of from 48 to 120 planes aloft during the daytime, orbiting in depth in a circle around Okinawa. Task Force 58, deployed just to the east of Okinawa, with its own picket group of from 6 to 8 destroyers, kept 13 carriers (7 CV and 6 CVL) on duty from 23 March to 27 April and a smaller number thereafter. Until 27 April from 14 to 18 converted carriers (CVE's) were in the area at all times, and until 20 April British Task Force 57, with 4 large and 6 converted carriers, remained off the Sakishima Islands to protect the southern flank. Two Marine Fighter Groups were installed and operating at Yontan and Kadena airfields by 9 April, and other Marine and Army Air Groups were added later. All assault antiaircraft artillery of the XXIV Corps was ashore by the night of 4 April, and that of III Amphibious Corps by 12 April. Japanese airmen were to find these combined defenses formidable.{177}

Enemy air opposition had been relatively light during the first few days after the landings. On 6 April the expected air reaction materialized with a fierce attack of 400 planes which had flown down from Kyushu to drive the invaders from Okinawa. The raids' began at dawn, and by noon Task Force 58 had shot down seven possible suicide planes. Throughout the afternoon the battle increased in intensity. Patrol and picket ships, which throughout the operation proved an irresistible attraction to enemy planes, were a favorite target. Japanese planes also appeared from time to time over the Hagushi beaches and transport area and were taken under fire by the ship and shore batteries. On such occasions the raider, ringed with bright streams of tracer bullets from automatic weapons, would streak across a sky filled with black puffs of smoke from hundreds of bursting shells, and in the course of seconds would plunge into the sea in a geyser of water and smoke, or crash into a ship with an even greater explosion of smoke and flame. Directed against such raiders, friendly fire killed four Americans and wounded thirty-four others in the XXIV Corps zone, ignited an ammunition dump near Kadena, destroyed an oil barge, and in the late afternoon shot down two American planes over the beaches. Some ships also suffered damage and casualties from friendly fire. Twenty-two of twenty-four suicide crashes were successful, sinking two destroyers, a mine sweeper, two ammunition ships, and an LST. A ship rescuing survivors from the lost LST was itself struck by a suicide plane soon after but was not seriously damaged. The attack cost the Japanese about 300 planes; 65 were splashed by fliers from the Essex alone. Unloading continued on the Hagushi beaches almost without pause, and the American fleet, although it had taken severe blows, was still intact.{178}

 

KAMIKAZE ATTACKS resulted in many hits, more near misses. U.S. S. Sangamon(above) was just missed but was hit in a later attack. Another near miss (below) sent U.S. battleship Missouri's gunners scurrying from upper turret while those in Turret 9 looked to see what was going on.