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Summary: The Battle of Okinawa, also known as Operation Iceberg, took place in April-June 1945. It was the largest amphibious landing in the Pacific theater of World War II. It also resulted in the largest casualties with over 100,000 Japanese casualties and 50,000 casualties for the Allies. This article gives an account of the 80 day plus battle for the Island of Okinawa which some have described as the “typhoon of steel”.


When two United States Marine and two Army divisions landed abreast on Okinawa on Easter Sunday, April 1, 1945, they faced an estimated 155,000 Japanese ground, air and naval troops holding an immense island on which an estimated 500,000 civilians lived in cities, towns and villages. Operation Iceberg was to be, in every way, vast when compared to any other operation undertaken by Allied forces in the Pacific War under U.S. Navy command. Indeed, using mainly divisions that had already undertaken island-hopping operations in the South and Central Pacific since mid-1942, the U.S. Pacific Fleet stood up the Tenth U.S. Army under Lieutenant General Simon Bolivar Buckner Jr., consisting of III Amphibious Corps and XXIV Army Corps — the largest land command ever assembled under the Navy’s direct control.

To those Japanese who thought the war was winnable, Okinawa was the last chance. The island lay within 350 miles — easy flight distance — from the Japanese homeland and was, by American design, to be the base from which the southernmost Home Island, Kyushu, would be pummeled to dust ahead of the expected follow-on invasion. Anything short of complete victory over Allied air, naval and ground forces spelled doom for Japan — and no such victory was remotely in the cards. Thus, from the Japanese view Okinawa was and could be no more than a delaying battle of attrition on a grand scale. The few Japanese who knew that their country’s war effort was in extremis were content to fight on Okinawa simply for reasons of honor, for all military logic pointed to the same dismal conclusion: Japan was vanquished in all but name as soon as the first Boeing B-29s left the ground in the Marianas, as soon as American carrier aircraft hit targets in Japan at will, as soon as even twin-engine bombers could strike Japanese ports from Iwo Jima, as soon as Japan dared not move a warship or cargo vessel from a port in any part of the shrinking empire for fear it would be sunk by an Allied submarine. By April 1, 1945, all those events were taking place routinely.

Although the Japanese commanders counted 155,000 defenders, of whom 100,000 were soldiers of Lt. Gen. Mitsuru Ushijima’s Thirty-second Army, the rest were of widely mixed abilities, and there were not nearly enough troops to cover the ground the way 23,000 troops had covered Iwo Jima. Therefore the forces on Okinawa were concentrated in a number of sectors that offered the best prospects for a robust, attritional defense. The northern half of the island was virtually conceded, and the south was turned into four extremely tough hedgehog defense sectors. The proportion of artillery and mortars to infantry was the highest encountered in the Pacific War.

Coming to put their defense arrangement to the test was the Tenth Army. The new 6th Marine Division (1st Provisional Marine Brigade plus the 29th Marines and attachments) would land over the northernmost beaches on the western side of Okinawa a little south of the island’s midpoint. It was to strike across the island, then turn north to pacify a little more than half of Okinawa on its own. To the right, the 1st Marine Division was also to strike across the island, then become part of the Tenth Army reserve. The Army’s 7th and 96th Infantry divisions were to land side by side in the southern half of the Tenth Army beachhead and pivot south to cover the width of the island. Also on April 1, the III Amphibious Corps’ (IIIAC) reserve, the 2nd Marine Division, made a feint toward a set of beaches in southeastern Okinawa. This feint was in line with where the Japanese predicted the main landing would take place, so for once a feint actually held large numbers of defenders in place looking the wrong way. Other units, including the Fleet Marine Force’s Pacific Reconnaissance Battalion, were assigned objectives elsewhere in the Ryukyu Islands, most of which were taken or at least assaulted before what was dubbed L-day on Okinawa.
(U.S. Marine Corps)
U.S. commanders observe their troops’ movements. Standing from left are Lt. Gen. Simon Bolivar Buckner Jr., commander of the Tenth Army; Maj. Gen. Lemuel Shepherd, commander of the 6th Marine Division; and his assistant commander, Brig. Gen. William T. Clement. Buckner was killed by a Japanese shell on June 18, 1945.

Immediate objectives were Yontan and Kadena airfields, in the IIIAC and XXIV Corps zones, respectively. As soon as these airfields could be brought to operational status, combat-support aircraft would operate from them. Also, many aircraft carriers would remain on station off Okinawa for as long as their air groups were needed. The land-based component was a Marine command named the Tactical Air Force and consisting of several Marine air groups of fighters and light bombers. Marine fighter squadrons based aboard fleet carriers and several new Marine carrier air groups (fighters and torpedo bombers) based aboard escort carriers would be available throughout the land operation.

The landings were made against zero opposition and with almost no casualties. Far from going into a state of optimism, however, the many veterans in the assault force realized that a very hard road lay before them, that the Japanese had chosen to dig deep and fight on their own terms.

Yontan Airfield fell by midmorning, after Marines overcame very light opposition along the juncture of the 1st and 6th Marine divisions. Reinforcements moved to fill gaps that developed due to rapid advances by the 4th, 7th and 22nd Marines. Marines of the 1st Division captured an intact bridge across a stream at the IIIAC-XXIV Corps boundary and overcame hastily built field fortifications all across the division front. Divisional and IIIAC artillery battalions landed routinely, and many batteries were providing fire by 1530 hours. The IIIAC advance halted between 1600 and 1700 to avoid more gaps and to help the Marines on the far right maintain contact with the 7th Infantry Division, whose left flank outpaced the 1st Marine Division right-flank unit by several hundred yards. The halt also gave artillery units outpaced by the rapid advance time to move forward and register night defensive fires.

Basically, all of L-day’s headaches arose from the light-to-nonexistent defensive effort, and not the usual spate of battle problems. Both airfields, Kadena and Yontan, were firmly in American hands by nightfall, and engineers were already at work to get them operational in the shortest possible time.
(U.S. Marine Corps)
A Marine Vought F4U-1D Corsair launches its wing-mounted rockets against Japanese targets on Okinawa. The Americans were using Okinawa’s airfields within days of their capture to support operations on the island.

While by no means a romp, the days that followed on L-day were nearly bloodless. Enemy troops were encountered here and there as the two Marine divisions swallowed up miles of territory against, at most, desultory opposition. Captives proved to be second- and third-rate troops, mostly technicians and other noncombatants drafted into ad hoc defensive units, lightly armed and miserably trained. Also, many thousands of civilians turned themselves in to Marines, to be passed along to temporary stockades in the rear. The most hard-pressed Marine units were engineers, then supply troops. Roads were barely discernible paths, so they had to be engineered for modern traffic, and many bridges had to be built over gullies and other breaks in the terrain. Even with roads in place, it was difficult to push supplies forward to the rapidly advancing ground units; they moved ahead thousands of yards a day and were constantly on the brink of outrunning their supply dumps. It was difficult, also, for artillery units to keep pace with the advance, and the infantry had a difficult time maintaining contact with flank units, because the advance tended to broaden an already broad front. By April 3, the Marine divisions were on ground slated to fall on L-plus-15.

As the advance continued with surprising ease, a picture slowly emerged from prisoner interrogations. The main Japanese effort had gone into deeply fortifying the southern portion of the island. The XXIV Corps ran into the outlying positions on April 4, on the phase line established for L-plus-10. But the Marines were oriented east and north, and swallowing miles of lightly defended ground each day. Before the two Marine divisions could join the fight in the south, they had to secure the rest of the island.

By April 4, the 1st Marine Division had completed its cross-island advance and had thus run out of objectives. It turned to scouring land already in its hands and building up its logistical base. By then, Japanese troops cut off in the IIIAC zone had begun to coalesce into what the Marines eventually characterized as guerrilla forces that lived off the land in wild areas and exploited opportunities to attack patrols and rear-area facilities. Such forces also appeared in the rear of the 6th Division. These so-called guerrillas had to be painstakingly tracked by Marine units far more suited for intense modern conflict. Fortunately for the Americans, although the Japanese guerrillas were well motivated, they were not trained for such operations and were easily hunted down if they showed themselves. To help quell civilian complicity in the guerrilla operation, several thousand Okinawan males were interned in camps beginning on April 11. The Tenth Army eventually clamped down on all civilians and filled eight internment camps in the IIIAC zone with Okinawans of all ages and both sexes. This seemed to end the problem of civilian aid to guerrilla operations, but those small groups of isolated Japanese soldiers continued to operate in diminished circumstances throughout most of the campaign.

The 6th Marine Division continued to drive north — literally driven on tanks and other vehicles. One reconnaissance force advanced 14 miles unopposed, then turned back to the main body. The 6th Engineer Battalion had a tough time widening and improving roads and replacing or bracing bridges at such a pace. On April 9, supplies began to come ashore on beaches much closer to the 6th Division front, and the 1st Armored Amtrac Battalion was committed to provide artillery support because the 15th Marines artillery battalions had such a difficult time keeping up with the rapidly moving infantry.

On April 7, Marine Air Group (MAG) 31 began to handle flight operations for its newly arrived squadrons at Yontan Airfield, and MAG-33 arrived on April 9. This relieved some of the ground-support burden on carrier air units, which were increasingly drawn into a battle of attrition with kamikaze units located in Japan and intermediate bases. Indeed, Marine air became almost wholly committed to XXIV Corps as it hit increasingly stiffer resistance in the south.

It took the 6th Marine Division until April 13 to locate a well-led, competent and powerful Japanese force — on Mount Yae Take, in extreme northern Okinawa. A four-day battle involving Marine air and artillery and naval gunfire support reduced the enemy force of 1,500 and opened the door for the final northern push, which was completed on April 20. The 6th Marine Division’s drive had cost 207 killed, 757 wounded and six missing by April 20, and the Marines had killed an estimated 2,000 Japanese troops.

Marine air, amply assisted by a sophisticated array of modern tools such as search, control and weather radars; landing force air-support control units equipped with advanced radio equipment; and frontline air control teams played a key role in supporting ground operations and forestalling kamikaze and conventional air attacks on the huge fleet that seemed to be a permanent fixture off Okinawa. Indeed, beginning on April 7, MAG-31 and MAG-33 fighter pilots scored hundreds of aerial victories off Okinawa, particularly in the north nearer to Japan. These included nocturnal kills by Marine squadrons equipped with F6F-5N Hellcat night fighters based ashore. Also, six Marine F4U Corsair squadrons were based aboard three fleet carriers, and they provided ground support and fleet cover. Indeed, Marine Corsairs took part in attacks on Kyushu airfields on March 18 and 19 that nearly swept kamikaze and conventional air units from the skies for several days. In return, Japanese aircraft damaged several American carriers, including USS Franklin, embarking two Marine F4U squadrons that saw a total of one day of offensive operations. By April 1945, Marine air was at the leading edge of technique and technology in support of modern combat operations across all three battle dimensions — land, sea and air.

The XXIV Corps met its first really stiff opposition on the southern front on April 6. Thereafter, resistance became more violent and better organized. The defenses extended across the entire width of the island and to an undetermined depth. In fact, it was a concentric defense, complete and pervasive, centered on the town of Shuri. Not apparent at the outset, but increasingly obvious with each passing day, the hard defenses could not and would not be carried by merely two Army divisions supported by organic and corps artillery, even after the artillery was bolstered on April 7 by IIIAC’s three 155mm gun battalions and three 155mm howitzer battalions — not to mention Marine air based at Yontan and whatever carrier air the fleet had on hand for ground support. Next, beginning on April 9, all four artillery battalions of the 11th Marines and two-thirds of the Army’s 27th Infantry Division were sent into the southern line, albeit with little effect.

By April 14, XXIV Corps had killed nearly 7,000 Japanese, but it had barely made a dent in the defenses north of Shuri. A corps attack on April 19 supported by 27 artillery battalions and 375 aircraft made negligible progress, then halted as the unperturbed Japanese troops moved back to their positions from underground shelters. The Army divisions advanced only after the Japanese withdrew from the advance defensive line on the night of April 23-24 to a more integrated line to the rear. On April 24, IIIAC was ordered to place one of its divisions in the Tenth Army reserve, and the 1st Marine Division was thus ordered to prepare to return to battle. (IIIAC’s third division, the 2nd, had been returned to Saipan to prepare for an amphibious assault near Okinawa that never took place.) On April 30, the 1st Marine Division advanced to replace the 27th Division in the XXIV Corps zone, and that Army division was ordered north to replace the 6th Marine Division so it could enter the southern battle.

The infantry units that the 1st Marine Division replaced had been ground down to regiments little larger than battalions, and battalions little larger than companies. Dead ahead was the bulk of a Japanese infantry division holding a defensive sector the island command had just reorganized to higher levels of lethality. On the division’s first full day on the line, the weather turned cool and rainy, a state that would prevail into July.
(U.S. Marine Corps)
Lieutenant General Isamu Cho was Ushijima’s chief of staff and committed suicide with his commander. Below: Marines use an Okinawan burial crypt for shelter during the fighting. Similar family burial places were located throughout the island, and many were put to use by the Marines.

The division went into the offensive on May 2, the westernmost of three divisions in the attack. The 5th Marines was stymied at the outset, but the adjacent 3rd Battalion, 1st Marines (3/1), fell into a gap. The 1st Marines attempted to change direction to exploit the gap, and 3/1 advanced even farther in the rain before nightfall. On the other hand, 1/1, on the division’s right, faced fierce opposition, and portions of the battalion that were cut off had to withdraw, after which 1/1 changed direction and won some new ground.

This baptismal day on the southern front was emblematic of the fighting that ensued. The Japanese made excellent use of broken ground and other natural cover, and the Marines were either stymied or fell into dead ground from which they could either advance or from which they had to withdraw to maintain a cohesive line against the uncanny knack the defenders showed for mounting enfilade movements. On May 3, the 5th Marines advanced more than 500 yards in its zone, but the 1st Marines was pinned down with heavy casualties, so the 5th had to pull back several hundred yards in places. There simply was no point at which the Marines could gain adequate leverage — the same scenario the replaced Army divisions had faced in their battle.

General Ushijima still held many thousands of first-line troops in reserve. These men had been tied down defending beaches in southeastern Okinawa for landings that never took place. As the Japanese gained a finer sense of American tactics, it was put to Ushijima that an offensive using these fresh, well-trained and well-equipped troops might chasten the Americans and buy a great deal of time and flexibility. Some of the fresh troops were fed into the defensive sectors to make good the losses of weeks of bitter attritional warfare, but the bulk were held back to cover the suspect beaches or to serve as a mobile reserve. By April 22, most of the fresh force was fed into the Shuri sector to stiffen its defenses. Ultimately, however, a number of Ushijima’s senior officers won an argument to launch a major tank-supported counteroffensive, including counterlandings behind American lines, that was to blunt the American offensive and perhaps throw it back.

Preceded by mass kamikaze attacks on rear areas on the island and logistical shipping offshore, the counteroffensive, including counterlandings on both coasts, began after dark on May 3. Artillery fire matched artillery fire at the front, while in the rear Marines opened fire on Japanese troops coming ashore on the beach on which Company B, 1/1, anchored the entire XXIV Corps line. This was not where the Japanese intended to land, and quick reaction by the defenders and confusion among the attackers created conditions for a Marine victory. Many more Marines were fed into the fire-lit battle, LVT(A)s (landing vehicles, tracked, assault) sealed the battlefield, and fresh troops hunted down infiltrators.

Forewarned by this landing attempt, Marines quelled other attempts farther up the coast. Army troops also defended successfully on the eastern coast.At dawn, behind an artillery curtain that never abated during the night and a rolling smoke barrage, the bulk of the Japanese Imperial Army’s battle-hardened 24th Infantry Division crashed into a curtain of fire erected in front of the 7th and 77th Infantry divisions by 12 155mm and 8-inch gun and howitzer battalions and tag-team air attacks that would mount up to 134 sorties by the day’s end. On May 4, the 1st Marine Division actually attacked in its zone in spite of Japanese efforts to win through to the east, but the division was stalled several hundred yards short of its objective line.

Far from delaying an American victory, the ill-advised Japanese counteroffensive used up the largest pool of seasoned fighters on the island, of which nearly 7,000 were killed. But other good fighters had remained in their excellent defensive sectors, and they showed no sign of cracking appreciably in the face of inexorable pressure across the entire corps front. In less than a week on the Shuri front, 649 Marines became casualties.

The 6th Marine Division began going into the southern line on May 7, squeezing in along the coast to the right of the 1st Marine Division, and IIIAC resumed control of both Marine divisions. From that point, despite interesting tactical embellishments, the battle to win Okinawa settled down to become a test of attritional theories, one based on attack and the other based on defense. The Japanese had the troops they had, and relatively few were trained infantry. The Americans had a larger pool of trained infantry, including ample replacements who, in the case of IIIAC, were used as logistical fillers until they were needed in the infantry battalions. Even then, attrition was high among all the American divisions — 11,147 replacements were fed into Marine infantry units on Okinawa — but when a Japanese veteran was killed, he could not be replaced.Deadly combinations of spirited infantry assaults, overwhelming artillery and naval gunfire support, and ample air support were played like a piano to advance American units through the rest of May and most of June. The concentric lines of defense built and held by the Japanese never got easier to reduce, but inexorably the quality of the troops holding them shifted downward, and they fell, one after the other.The 2nd Marine Division’s 8th Marine Regiment took part in several landings on islands elsewhere in the Ryukyus in late May, then went ashore on Okinawa to fill out the 1st Marine Division for the final assaults of the campaign. An interesting footnote to Marine Corps history came about on June 18 when the Tenth Army commander, General Buckner, was killed by a Japanese artillery shell in the 8th Marines line while reconnoitering the front.

The next senior general officer on the scene was Marine Maj. Gen. Roy Geiger, the IIIAC commanding general. Geiger, an aviator who had commanded the 1st Marine Aircraft Wing at Guadalcanal, I Marine Amphibious Corps at Bougainville and IIIAC at Guam and Okinawa, was spot-promoted to lieutenant general to become the first and only Marine and the first and only naval aviator — perhaps the first and only aviator — ever to command an American army in the field.The Japanese defenses were all but overwhelmed by June 16, and Ushijima realized that the end was near. On June 19, he dissolved his staff and ordered all available troops to go over to guerrilla operations. On June 21, organized resistance came to an end in the 6th Marine Division zone, which encompassed the southern shore of the island. By then, Japanese troops were surrendering by the hundreds.

The 1st Marine Division mounted its final attacks of the campaign, also on June 21, and reported by nightfall that all its objectives had been secured. The XXIV Corps made similar announcements. It thus fell to General Geiger to declare Okinawa secure following a bloody 82-day battle. The final official flag-raising ceremony on a Pacific War battlefield took place at the Tenth Army headquarters at 1000 hours, June 22, 1945. Earlier that morning, Ushijima and his chief of staff, Lt. Gen. Isamu Cho, committed ritual suicide. The battle had been among the most brutal of the Pacific War. The Navy suffered its greatest casualties for a single engagement. More than 12,000 Americans were killed and a further 50,000 were wounded. More than 150,000 Japanese — many of them civilians — were killed during the battle. Despite the casualties, preparations were quickly underway for the long-anticipated invasion of Japan. All hands turned to in order to begin preparations to invade Kyushu. Already, Army Air Forces bomber groups that had been in Europe on V-E Day joined Marine Tactical Air Force units operating from Okinawa’s airfields and thousands of American, British and Canadian carrier-based aircraft in the pre-landing bombardment that was to lay waste to the southernmost Home Island before a contemplated October invasion was set in motion.Who could have known on June 22, 1945, that only some six weeks separated America’s Pacific warriors from the blinding flashes over Hiroshima and Nagasaki that would send the vast majority home to the peace so many of their brave comrades had died to secure.

This article was written by Eric Hammel, a noted historian of the Pacific War. This article is adapted from his forthcoming book, Pacific Warriors: The U.S. Marines in World War II, A Pictorial Tribute, published by Zenith Press. This article originally appeared in the June 2005 issue of World War II magazine. For more great articles subscribe to World War II magazine today!