On 22 March 1945, the last of the 180,000 men of the US Tenth Army, under US Army Lt Gen Simon Bolivar Buckner were loaded onto transports. The final ships bearing the US 1st, 2nd, and 6th Marine Divisions, and US Army’s 7th, 27th, 77th, and 96th Infantry Divisions departed the Ulithi atoll on the 1400 ships of the US Fifth Fleet that afternoon for the trip to Okinawa in the Ryukyu Islands. The US Tenth Army was the largest land force under direct US Navy command in American history. On 26 March, the US Fifth Fleet arrived off Okinawa. That morning, the US 77th Infantry Division seized the Kerama Islands just west of Okinawa for an anchorage to support the main landings, and protect the vulnerable transports from small Kamikaze suicide boats.

On Easter Sunday, 1 April 1945, the US Army XXIV Corps, and US Marine III Amphibious Corps landed on the eastern shores of Okinawa to complete silence.

On paper the Japanese 32nd Army under Gen Mitsuru Ushijima had over 150,000 soldiers to defend the island of Okinawa, including tens of thousands of drafted Okinawan civilians, and thousands of school children shamed into volunteering. The number wasn’t nearly enough to cover the entire island as the Japanese did at Iwo Jima. Okinawa is 22 times the size of Iwo Jima, so Ushijima decided to defend, Peleliu style, at choke points and successive fortified lines across the southern half of the island. The Americans landed against no opposition.

The Americans seized the Kadena and Yontan airfields by nightfall. The US Tenth Army was the only US Army in the war to have its own dedicated air force, and it flew off of those air fields every minute of day light for the next 80 days. By 4 April, the Marines controlled the northern half of the island, with only small Japanese stay behind troops conducting guerilla warfare in the Marine rear areas. The Marines only finally defeated the guerillas once all Okinawan civilians in their sector were herded into internment camps. Without civilian support, the Japanese hold outs were all hunted down by the end of the campaign. The last organized Japanese force in northern Okinawa fought to the death on Mount Yae Take on 20 April.

On 16 April, the 77th Infantry Division conducted another amphibious invasion, this time the island Ie Shima. The fighting on Ie Shima was fiecre and included hand to hand combat with Japanese civilians, including women and children, armed with spears. Famed war correspondent Ernie Pyle was killed on Ie Shima when a Japanese machine gun ambushed his jeep as he drove to the front with one 77th’s regimental commanders. A burst caught him in the forehead and he was buried on the island with the rest of the 77th’s casualties. The 77th erected a small monument, which still stands, that reads, “At this spot the 77th Infantry Division lost a buddy, Ernie Pyle, 18 April 1945.”
Though the fighting in the north was tough, the battle for southern Okinawa was in an entirely different level of Hell. The XXIV Corps was stopped cold in the broken ground north of Shuri. The defenses extended the width of Okinawa and there was nowhere for the Americans to go except into the teeth of Ushijima’s defenses. The Americans only took the Japanese advanced line when its defenders retired to the main line of resistance just a bit further south. The Army divisions were fought out by 24 April and the relatively fresh Marines of the III Amphibious Corps were sent south.

On 2 May, the skies turned cloudy and it started raining. It would stay that way until July. That same day, the Marines went on the offensive. They made almost no progress despite fierce fighting and several potential breakthroughs. The Japanese didn’t just defend, they counter attacked using tunnels and defilades in the broken terrain to move troops to the flank or even behind the Marines. Ushijima had thousands of fresh troops that were guarding southern beaches which were obviously not going to see a landing. Several Marine companies were cut off and nearly annihilated before they fought their way out of their entrapments.

The successful defense on 2-3 May against the Marines convinced Ushijima’s subordinates to pressure him into a large scale attack with tanks and beach landings behind the Marines. Ushijima knew he could not win the Battle of Okinawa, but he did believe that every day he held the Americans on Okinawa was another day that the Home Islands could prepare for their inevitable invasion. He had an entire veteran division in reserve and wanted to use them bleeding the Americans in the naturally defensible terrain of the island. But his subordinates demanded that they attack lest they lose face. Ushijima gave in.

The Japanese counter offensive was initially a complete surprise, but the landings and assaults were quickly isolated and destroyed. As Ushijima had foreseen, the offensive was a complete waste of men; men he had no way to replace. Nonetheless, for the next 45 days, the Americans ground down the Japanese in brutal attritional warfare. The superior Japanese positions endured a seemingly inexhaustible supply of American firepower. An example of the brutal and ruthless nature of the fighting was Sugar Loaf Hill, a bare 15m high bald hill that was initially a company objective for the 29th Marines. Sugar Loaf anchored the far end of the Shuri Line. Eleven assaults over seven days, 12-18 May, by three different marine regiments consumed nearly 5000 American casualties, and killed 2500 Japanese. Most American wounded at Sugar Loaf never saw a Japanese soldier. But every American casualty could be replaced while the quality of the Japanese defenders declined. On 29 May the Shuri Line was broken when the Marines secured Shuri Castle.

The remaining 30,000 troops of the 32nd Army withdrew to the Kiyan peninsula for a last stand. By this point in the battle, cut off Japanese troops were committing suicide by the thousands. A Marine landing on the peninsula resulted in nearly 1200 Japanese sailors committing suicide when they were cut off below ground. As the situation for the Japanese became untenable, the Japanese soldiers began demanding of Japanese civilians that they too commit suicide. Corrupted by propaganda that the American were going to rape and kill them anyway, many did. The sound of a grenade going off in an underground bunker was a common occurrence, and thousands of Japanese civilians jumped from the southern cliffs to avoid capture. Of the 300,000 pre-battle civilian population of Okinawa, over 100,000 were dead by mid-June, mostly by suicide.

On 18 June, while checking on troops, Buckner was killed by Japanese artillery fire and became the highest ranking American officer killed by enemy fire in the war. He was replaced by Marine Major General Roy Geiger before he was replaced by Gen Joseph Stilwell, who was in the Philippines returning from China when Buckner was killed.

On 21 June, Ushijima ordered his remaining troops to disperse and conduct guerilla operations. He committed seppuku the next day, but not before ordering his aide, Colonel Yahara, to stay alive to tell the Japanese side of the story. Yahara was the senior Japanese officer to survive Okinawa. About 14,000 Japanese soldiers surrendered during the Battle for Okinawa, but almost all were Okinawan or Japanese mainland civilians drafted just before the battle. The Americans suffered 14,000 dead and 50,000 wounded in the Battle of Okinawa, more than in the Battle of the Bulge in Europe, the largest American battle in history.

The ferocity of the Japanese defense, the American casualties, and the mass suicide of Japanese civilians on Okinawa (and the specter of a post war conflict with the Soviet Union) convinced President Truman to authorize the use of atomic bombs against Japan in lieu of direct invasion. The planners of Operation Downfall, the invasion of the Japanese Home Islands, and its two subordinate operations, Operation Olympic: the invasion Kyushu, and Operation Coronet: the invasion of Honshu had projected more than a million Allied casualties subduing Japan. Truman said, “I do not want another Okinawa from one end of Japan to the other.” The first atomic bomb was dropped on Hiroshima on 6 August, 1945, and another on Nagasaki three days later on 9 August. Emperor Hirohito announced Japan’s surrender on 15 August 1945.