Allied

In all, the US Army had over 103,000 soldiers (of these, 38,000+ were non-divisional artillery, combat support and HQ troops, with another 9,000 service troops),^[34]: 39 over 88,000 Marines and 18,000 Navy personnel (mostly Seabees and medical personnel).^[34]: 40 At the start of the Battle of Okinawa, the US Tenth Army had 182,821 personnel under its command.^[34]: 40 It was planned that Lieutenant General Simon Bolivar Buckner Jr. would report to Vice Admiral Richmond K. Turner until the amphibious phase was completed, after which he would report directly to Admiral Raymond A. Spruance. Total aircraft in the US Navy, Marine and Army Air Force exceeded 3,000 over the course of the battle, including fighters, attack aircraft, scout planes, bombers and dive-bombers. The invasion was supported by a fleet consisting of 18 battleships, 27 cruisers, 177 destroyers/destroyer escorts, 39 aircraft carriers (11 fleet carriers, 6 light carriers and 22 escort carriers) and various support and troop transport ships.^[35]

The British naval contingent accompanied 251 British naval aircraft and included a British Commonwealth fleet with Australian, New Zealand and Canadian ships and personnel.^[36]

Japanese

The Japanese land campaign (mainly defensive) was conducted by the 67,000-strong (77,000 according to some sources) regular 32nd Army and some 9,000 Imperial Japanese Navy troops at Oroku Naval Base (only a few hundred of whom had been trained and equipped for ground combat), supported by 39,000 drafted local Ryukyuan people (including 24,000 hastily drafted rear militia called Boeitai and 15,000 non-uniformed laborers). The Japanese had used kamikaze tactics since the Battle of Leyte Gulf, but for the first time they became a major part of the defense. Between the American landing on 1 April and 25 May, seven major kamikaze attacks were attempted, involving more than 1,500 planes.

The 32nd Army initially consisted of the 9th, 24th and 62nd Divisions and the 44th Independent Mixed Brigade. The 9th Division was moved to Taiwan before the invasion, resulting in shuffling of Japanese defensive plans. Primary resistance was to be led in the south by Lieutenant General Mitsuru Ushijima, his chief of staff, Lieutenant General Isamu Chō and his chief of operations, Colonel Hiromichi Yahara. Yahara advocated a defensive strategy, whilst Chō advocated an offensive one.

In the north, Colonel Takehido Udo was in command. The naval troops were led by Rear Admiral Minoru Ōta. They expected the Americans to land 6–10 divisions against the Japanese garrison of two and a half divisions. The staff calculated that superior quality and numbers of weapons gave each US division five or six times the firepower of a Japanese division. To this, would be added the Americans' abundant naval and air firepower.

Operation Ten-Go

Operation Ten-Go (Ten-gō sakusen) was the attempted attack by a strike force of 10 Japanese surface vessels, led by Yamato and commanded by Admiral Seiichi Itō. This small task force had been ordered to fight through enemy naval forces, then beach Yamato and fight from shore, using her guns as coastal artillery and her crew as naval infantry. The Ten-Go force was spotted by submarines shortly after it left the Japanese home waters and was intercepted by US carrier aircraft.

Under attack from more than 300 aircraft over a two-hour span, the world's largest battleship sank on 7 April 1945 after a one-sided battle, long before she could reach Okinawa. (US torpedo bombers were instructed to aim for only one side to prevent effective counter flooding by the battleship's crew, and to aim for the bow or the stern where armor was believed to be the thinnest.) Of Yamato's screening force, the light cruiser Yahagi and 4 of the 8 destroyers were also sunk. The Imperial Japanese Navy lost some 3,700 sailors, including Admiral Itō, at the cost of 10 US aircraft and 12 airmen.

British Pacific Fleet

The British Pacific Fleet, taking part as Task Force 57, was assigned the task of neutralizing the Japanese airfields in the Sakishima Islands, which it did successfully from March 26 to April 10. On April 10, its attention was shifted to airfields in northern Formosa. The force withdrew to San Pedro Bay on April 23. On May 1, the British Pacific Fleet returned to action, subduing the airfields as before, this time with naval bombardment as well as aircraft. Several kamikaze attacks caused significant damage, but as the Royal Navy carriers had armored flight decks, they experienced only a brief interruption to their force's operations.^[41][42]

• Royal Navy Fleet Air Arm Avengers, Seafires and Fireflies on HMS Implacable warm up their engines before taking off.
• HMS Formidable on fire after a kamikaze attack on May 4. The ship was out of action for fifty minutes.

Northern Okinawa

The main landing was made by the XXIV Corps and the III Amphibious Corps on the Hagushi beaches on the western coast of Okinawa on 1 April. The 2nd Marine Division conducted a demonstration off the Minatoga beaches on the southeastern coast to deceive the Japanese about American intentions and delay movement of reserves from there.^{[16]: 68–74}

Tenth Army swept across the south-central part of the island with relative ease, capturing the Kadena and the Yomitan airbases within hours of the landing.^{[24]: 67–69 [16]: 74–75} In light of the weak opposition, General Buckner decided to proceed immediately with Phase II of his plan, the seizure of northern Okinawa. The 6th Marine Division headed up the Ishikawa Isthmus and by 7 April had sealed off the Motobu Peninsula.^{[16]: 138–141}

Six days later on 13 April, the 2nd Battalion, 22nd Marine Regiment, reached Hedo Point at the northernmost tip of the island. By this point, the bulk of the Japanese forces in the north (codenamed Udo Force) were cornered on the Motobu Peninsula. The terrain was mountainous and wooded, with the Japanese defenses concentrated on Mount Yaedake, a twisted mass of rocky ridges and ravines on the center of the peninsula. There was heavy fighting before the Marines finally cleared Yaedake on 18 April.^{[16]: 141–148} However, this was not the end of ground combat in northern Okinawa. On 24 May, the Japanese mounted Operation Gi-gou: a company of Giretsu Kuteitai commandos were airlifted in a suicide attack on Yomitan. They destroyed 70,000 US gallons (260,000 L) of fuel and nine planes before being killed by the defenders, who lost two men.

Meanwhile, the 77th Infantry Division assaulted Ie Shima, a small island off the western end of the peninsula, on 16 April. In addition to conventional hazards, the 77th Infantry Division encountered kamikaze attacks and even local women armed with spears. There was heavy fighting before the area was declared secured on 21 April and became another airbase for operations against Japan.^{[16]: 149–183}

Southern Okinawa

While the 6th Marine Division cleared northern Okinawa, the US Army 96th and 7th Infantry Divisions wheeled south across the narrow isthmus of Okinawa. The 96th Infantry Division began to encounter fierce resistance in west-central Okinawa from Japanese troops holding fortified positions east of Highway No. 1 and about 5 mi (8 km) northwest of Shuri, from what came to be known as Cactus Ridge.^{[16]: 104–105} The 7th Infantry Division encountered similarly fierce Japanese opposition from a rocky pinnacle located about 1,000 yd (910 m) southwest of Arakachi (later dubbed "The Pinnacle"). By the night of 8 April, American troops had cleared these and several other strongly fortified positions. They suffered over 1,500 battle casualties in the process while killing or capturing about 4,500 Japanese. Yet the battle had only begun, for it was realized that "these were merely outposts," guarding the Shuri Line.^{[16]: 105–108}

The next American objective was Kakazu Ridge (26.259°N 127.737°E / 26.259; 127.737), two hills with a connecting saddle that formed part of Shuri's outer defenses. The Japanese had prepared their positions well and fought tenaciously. The Japanese soldiers hid in fortified caves. American forces often lost personnel before clearing the Japanese out from each cave or other hiding place. The Japanese sent Okinawans at gunpoint out to obtain water and supplies for them, which led to civilian casualties. The American advance was inexorable but resulted in a high number of casualties on both sides.^{[16]: 110–125}

As the American assault against Kakazu Ridge stalled, Lieutenant General Ushijima—influenced by General Chō—decided to take the offensive. On the evening of 12 April, the 32nd Army attacked American positions across the entire front. The Japanese attack was heavy, sustained, and well organized. After fierce close combat, the attackers retreated, only to repeat their offensive the following night. A final assault on 14 April was again repulsed. The effort led the 32nd Army's staff to conclude that the Americans were vulnerable to night infiltration tactics but that their superior firepower made any offensive Japanese troop concentrations extremely dangerous, and they reverted to their defensive strategy.^{[16]: 130–137}

The 27th Infantry Division, which had landed on 9 April, took over on the right, along the west coast of Okinawa. General John R. Hodge now had three divisions in the line, with the 96th in the middle and the 7th to the east, with each division holding a front of only about 1.5 mi (2.4 km). Hodge launched a new offensive on 19 April with a barrage of 324 guns, the largest ever in the Pacific Ocean Theater. Battleships, cruisers, and destroyers joined the bombardment, which was followed by 650 Navy and Marine planes attacking the Japanese positions with napalm, rockets, bombs, and machine guns. The Japanese defenses were sited on reverse slopes, where the defenders waited out the artillery barrage and aerial attack in relative safety, emerging from the caves to rain mortar rounds and grenades upon the Americans advancing up the forward slope.^{[16]: 184–194}

A tank assault to achieve breakthrough by outflanking Kakazu Ridge failed to link up with its infantry support attempting to cross the ridge and therefore failed with the loss of 22 tanks. Although flame tanks cleared many cave defenses, there was no breakthrough, and the XXIV Corps suffered 720 casualties. The losses might have been greater except for the fact that the Japanese had practically all of their infantry reserves tied up farther south, held there by another feint off the Minatoga beaches by the 2nd Marine Division that coincided with the attack.^{[16]: 196–207}

At the end of April, after Army forces had pushed through the Machinato defensive line,^[43] the 1st Marine Division relieved the 27th Infantry Division and the 77th Infantry Division relieved the 96th. When the 6th Marine Division arrived, the III Amphibious Corps took over the right flank and Tenth Army assumed control of the battle.^[16]: 265

On 4 May, the 32nd Army launched another counter-offensive. This time, Ushijima attempted to make amphibious assaults on the coasts behind American lines. To support his offensive, the Japanese artillery moved into the open. By doing so, they were able to fire 13,000 rounds in support, but effective American counter-battery fire destroyed dozens of Japanese artillery pieces. The attack failed.^{[16]: 283–302}

Buckner launched another American attack on 11 May. Ten days of fierce fighting followed. On 13 May, troops of the 96th Infantry Division and 763rd Tank Battalion captured Conical Hill (26.21°N 127.75°E / 26.21; 127.75). Rising 476 ft (145 m) above the Yonabaru coastal plain, this feature was the eastern anchor of the main Japanese defenses and was defended by about 1,000 Japanese. Meanwhile, on the opposite coast, the 1st and 6th Marine Divisions fought for "Sugar Loaf Hill" (26.222°N 127.696°E / 26.222; 127.696). The capture of these two key positions exposed the Japanese around Shuri on both sides. Buckner hoped to envelop Shuri and trap the main Japanese defending force.^{[16]: 311–359}

By the end of May, monsoon rains which had turned contested hills and roads into a morass exacerbated both the tactical and medical situations. The ground advance began to resemble a World War I battlefield, as troops became mired in mud, and flooded roads greatly inhibited evacuation of wounded to the rear. Troops lived on a field sodden by rain, part garbage dump and part graveyard. Unburied Japanese and American bodies decayed, sank in the mud and became part of a noxious stew. Anyone sliding down the greasy slopes could easily find their pockets full of maggots at the end of the journey.^{[16]: 364–370}

From 24 to 27 May the 6th Marine Division cautiously occupied the ruins of Naha, the largest city on the island, finding it largely deserted.^{[16]: 372–377}

On 26 May aerial observers saw large troop movements just below Shuri. On 28 May Marine patrols found recently abandoned positions west of Shuri. By 30 May the consensus among Army and Marine intelligence was that the majority of Japanese forces had withdrawn from the Shuri Line.^{[16]: 391–392} On 29 May the 1st Battalion, 5th Marines (1/5 Marines) occupied high ground 700 yards (640 m) east of Shuri Castle and reported that the castle appeared undefended. At 10:15 Company A, 1/5 Marines occupied the castle.^{[16]: 395–496}

Shuri Castle had been shelled by the battleship USS Mississippi for three days before this advance.^[44] The 32nd Army withdrew to the south and thus the Marines had an easy task of securing Shuri Castle.^[44][45] The castle, however, was outside the 1st Marine Division's assigned zone, and only frantic efforts by the commander and staff of the 77th Infantry Division prevented an American airstrike and artillery bombardment which would have resulted in many friendly fire casualties.^[16]: 396

On 29 May a Confederate flag was raised over Shuri Castle,^[46] before being removed and replaced by a US flag three days later on orders of General Buckner.^[47]

The Japanese retreat, although harassed by artillery fire, was conducted with great skill at night and aided by the monsoon storms. The 32nd Army was able to move nearly 30,000 personnel into its last defense line on the Kiyan Peninsula, which ultimately led to the greatest slaughter on Okinawa in the latter stages of the battle, including the deaths of thousands of civilians. In addition, there were 9,000 IJN troops supported by 1,100 militia, with approximately 4,000 holed up at the underground headquarters on the hillside overlooking the Okinawa Naval Base in the Oroku Peninsula, east of the airfield.^{[16]: 392–394}

On 4 June, elements of the 6th Marine Division launched an amphibious assault on the peninsula. The 4,000 Japanese sailors, including Admiral Ōta, all committed suicide within the hand-built tunnels of the underground naval headquarters on 13 June.^{[16]: 427–434} By 17 June, the remnants of Ushijima's shattered 32nd Army were pushed into a small pocket in the far south of the island to the southeast of Itoman.^{[16]: 455–4661}

On 18 June, General Buckner was killed by Japanese artillery fire while monitoring the progress of his troops from a forward observation post. Buckner was replaced by Major General Roy Geiger. Upon assuming command, Geiger became the only US Marine to command a numbered army of the US Army in combat; he was relieved five days later by General Joseph Stilwell. On 19 June, Brigadier General Claudius Miller Easley, the commander of the 96th Infantry Division, was killed by Japanese machine-gun fire, also while checking on the progress of his troops at the front.^[16]: 461

The last remnants of Japanese resistance ended on 21 June, although some Japanese continued hiding, including the future governor of Okinawa Prefecture, Masahide Ōta.^[48] Ushijima and Chō committed suicide by seppuku in their command headquarters on Hill 89 in the closing hours of the battle.^{[16]: 468–471} Colonel Yahara had asked Ushijima for permission to commit suicide, but the general refused his request, saying: "If you die there will be no one left who knows the truth about the battle of Okinawa. Bear the temporary shame but endure it. This is an order from your army commander."^[38]: 723 Yahara was the most senior officer to have survived the battle on the island, and he later authored a book titled The Battle for Okinawa. On 22 June Tenth Army held a flag-raising ceremony to mark the end of organized resistance on Okinawa. On 23 June a mopping-up operation commenced, which concluded on 30 June.^{[16]: 471–473}

On 15 August 1945, Admiral Matome Ugaki was killed while part of a kamikaze raid on Iheyajima island. The official surrender ceremony was held on 7 September, near the Kadena Airfield.

Military losses

Civilian losses, suicides, and atrocities

Some of the other islands that saw major battles in World War II, such as Iwo Jima, were uninhabited or had been evacuated. Okinawa, by contrast, had a large indigenous civilian population; US Army records from the planning phase of the operation made the assumption that Okinawa was home to about 300,000 civilians. The official US Tenth Army count for the 82-day campaign is a total of 142,058 recovered enemy bodies (including those civilians pressed into service by the Imperial Japanese Army), with the deduction made that about 42,000 were non-uniformed civilians who had been killed in the crossfire. Okinawa Prefecture's estimate is over 100,000 losses.^[82]

During the battle, American forces found it difficult to distinguish civilians from soldiers. It became common for them to shoot at Okinawan houses, as one infantryman wrote:

There was some return fire from a few of the houses, but the others were probably occupied by civilians—and we didn't care. It was a terrible thing not to distinguish between the enemy and women and children. Americans always had great compassion, especially for children. Now we fired indiscriminately.^[83]

In its history of the war, the Okinawa Prefectural Peace Memorial Museum^[82] presents Okinawa as being caught between Japan and the United States. During the battle, the Imperial Japanese Army showed indifference to Okinawans' safety, and its soldiers used civilians as human shields or outright killed them. The Japanese military also confiscated food from the Okinawans and executed those who hid it, leading to mass starvation, and forced civilians out of their shelters. Japanese soldiers also killed about 1,000 people who spoke in the Okinawan language to suppress spying.^[84] The museum writes that "some were blown apart by [artillery] shells, some finding themselves in a hopeless situation were driven to suicide, some died of starvation, some succumbed to malaria, while others fell victim to the retreating Japanese troops."^[82]

With the impending Japanese defeat, civilians often committed mass suicide, urged on by the Japanese soldiers who told locals that victorious American soldiers would go on a rampage of killing and raping. Ryūkyū Shimpō, one of the two major Okinawan newspapers, wrote in 2007: "There are many Okinawans who have testified that the Japanese Army directed them to commit suicide. There are also people who have testified that they were handed grenades by Japanese soldiers" to blow themselves up.^[85] Thousands of civilians, having been induced by Japanese propaganda to believe that American soldiers were barbarians who committed horrible atrocities, killed their families and themselves to avoid capture at the hands of the Americans. Some of them threw themselves and their family members from the southern cliffs where the Peace Museum now resides.^[86]

Okinawans "were often surprised at the comparatively humane treatment they received from the American enemy".^[87][88] Islands of Discontent: Okinawan Responses to Japanese and American Power by Mark Selden states that the Americans "did not pursue a policy of torture, rape, and murder of civilians as Japanese military officials had warned".^[89] American Military Intelligence Corps^[90] combat translators such as Teruto Tsubota managed to convince many civilians not to kill themselves.^[91] Survivors of the mass suicides blamed also the indoctrination of their education system of the time, in which the Okinawans were taught to become "more Japanese than the Japanese" and were expected to prove it.^[92]

Witnesses and historians claim that soldiers, mainly Japanese troops, raped Okinawan women during the battle. Rape by Japanese troops reportedly "became common" in June, after it became clear that the Imperial Japanese Army had been defeated.^{[32][16]: 462} Marine Corps officials in Okinawa and Washington have said that they knew of no rapes by American personnel in Okinawa at the end of the war.^[93] There are, however, numerous credible testimony accounts which note that a large number of rapes were committed by American forces during the battle. This includes stories of rape after trading sexual favors or even marrying Americans,^[94] such as the alleged incident in the village of Katsuyama, where civilians said they had formed a vigilante group to ambush and kill three black American soldiers who they claimed would frequently rape the local girls there.^[95]

Effect on the wider war

Because the next major event following the Battle of Okinawa was the total surrender of Japan, the effect of this battle is more difficult to consider. Because Japan surrendered when it did, the anticipated series of battles and the invasion of the Japanese homeland never occurred, and all military strategies on both sides which presupposed this apparently-inevitable next development were immediately rendered moot.

Some military historians believe that the Okinawa campaign led directly to the atomic bombings of Hiroshima and Nagasaki, as a means of avoiding the planned ground invasion of the Japanese mainland. This view is explained by Victor Davis Hanson in his book Ripples of Battle:

... because the Japanese on Okinawa ... were so fierce in their defense (even when cut off and without supplies), and because casualties were so appalling, many American strategists looked for an alternative means to subdue mainland Japan, other than a direct invasion. This means presented itself, with the advent of atomic bombs, which worked admirably in convincing the Japanese to sue for peace [unconditionally], without American casualties.

Meanwhile, many parties continue to debate the broader question of "why Japan surrendered", attributing the surrender to a number of possible reasons including: the atomic bombings,^{[112][113][114]} the Soviet invasion of Manchuria,^[115][116] and Japan's depleted resources.^{[117][page needed][118]}

Memorial

In 1995, the Okinawa government erected a memorial monument named the Cornerstone of Peace in Mabuni, the site of the last fighting in southeastern Okinawa.^[119] The memorial lists all the known names of those who died in the battle, civilian and military, Japanese and foreign. As of 2022, the monument lists 241,686 names.^[120]

Modern US base

Significant US forces remain garrisoned on Okinawa as the United States Forces Japan, which the Japanese government sees as an important guarantee of regional stability,^[121] and Kadena remains the largest US air base in Asia. Local residents have long protested against the size and presence of the base.^[122]