The land battle took place over about 81 days beginning on 1 April 1945.
The first Americans ashore were soldiers of the 77th Infantry Division who landed in the Kerama Islands, 15 mi (24 km) west of Okinawa on 26 March.
Subsidiary landings followed, and the Kerama group was secured over the next five days.
In these preliminary operations, the 77th Infantry Division suffered 27 dead and 81 wounded, while the Japanese dead and captured numbered over 650.
The operation provided a protected anchorage for the fleet and eliminated the threat from suicide boats.
On 31 March, Marines of the Amphibious Reconnaissance Battalion landed without opposition on Keise Shima, four islets just 8 mi (13 km) west of the Okinawan capital of Naha.
A group of 155 mm (6.1 in) "Long Tom" artillery pieces went ashore on the islets to cover operations on Okinawa.
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.
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.
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.
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.[
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.
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.
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.[10]: 105–108
The next American objective was Kakazu Ridge (26.259°N 127.737°E), 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.
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.
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.
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.
At the end of April, after Army forces had pushed through the Machinato defensive line, 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.
Lt. Col. Richard P. Ross Jr., commander of 3rd Battalion, 1st Marines braves sniper fire to place the United States' colors over the parapets of Shuri Castle on 30 May. This flag was first raised over Cape Gloucester and then Peleliu. A Japanese prisoner of war sits behind barbed wire after he and 306 others were captured within the last 24 hours of the battle by 6th Marine Division.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.
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). 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). 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.
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.
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.
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.
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.
Shuri Castle had been shelled by the battleship USS Mississippi for three days before this advance.
The 32nd Army withdrew to the south and thus the Marines had an easy task of securing Shuri Castle.
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.
On 29 May a Confederate flag was raised over Shuri Castle, before being removed and replaced by a US flag three days later on orders of General Buckner.
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.
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.
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.
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.
The last remnants of Japanese resistance ended on 21 June, although some Japanese continued hiding, including the future governor of Okinawa Prefecture, Masahide Ōta.[36] Ushijima and Chō committed suicide by seppuku in their command headquarters on Hill 89 in the closing hours of the battle.
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.
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.
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.