Key point: The battle would greatly influence American war planning going forward.
To the Americans, Okinawa represented a major stepping-stone toward the final defeat of the Japanese Empire. The successful occupation of the island by American forces would provide air bases and naval facilities that would allow for attacks on the Home Islands themselves. To the Japanese, the surrender of a base so close to the heart of the empire would seriously compromise the ability of their armed forces to defend the homeland. Capture of the island would also interdict the critical flow of petroleum to Japan from Borneo, Sumatra, and Burma.
Okinawa is the largest and most densely populated island in the Ryukyu chain, some 380 miles southwest of the Japanese Home Island of Kyushu. With a total area of 485 square miles, Okinawa is approximately 60 miles long with a width of 2 to 18 miles. The island’s northeastern area is very rugged, mountainous, wooded, and lightly populated.
In 1945 the population of Okinawa was estimated to be approximately 500,000, two-thirds of whom lived in the southern one-third of the island. Unlike the north, the south had large open areas suitable for cultivation. Before World War II, the Okinawans maintained a largely rural, agricultural society. The islanders fished and raised sugar cane, sweet potatoes, rice, and soybeans. They tended to concentrate in small villages rather than in large cities. Ancestor worship dominated their religious practices, and the tombs of those ancestors dotted the countryside.
The Japanese on Kyushu regarded the Okinawans as their inferiors. The Okinawans were a blend of Japanese, Malay, and Chinese ancestry. Although they spoke a Japanese dialect, communication between the two groups often remained strained. Okinawan labor provided most of the manpower for the construction of the elaborate system of defenses erected by the Imperial Japanese Army.
Why did the islanders support the Japanese occupiers? First, the Army dealt brutally with anyone failing to cooperate. Second, the Japanese told the Okinawans that rape, torture, and even death would be their fate once they fell into the hands of the American Army. The Japanese Army also did everything it could psychologically to discourage civilians from surrendering to the Americans in the forthcoming campaign. They even advocated suicide by the noncombatants as the alternative to what they considered to be a dishonorable capitulation.
The sudden loss of the Japanese bases in the Marianas—Guam, Saipan, and Tinian—and the destruction of the Japanese 31st Army there in July 1944 necessitated the strengthening of defenses in the Ryukyu island chain, Okinawa in particular. Imperial Headquarters created the 32nd Army, led by three crack divisions—the 9th, 24th, and 62nd—a force that would ultimately consist of over 110,000 men in infantry, artillery, engineers, and communications units, as well as naval and aviation personnel. Included in that number were 24,000 Okinawan males of the Home Guard, conscripted into the 32nd, whether they were willing or not. Some individual Okinawans were incorporated into the veteran Japanese infantry units as well. The original strategy called for defense against any invading force by Japanese air and naval units during the attempted landings, followed by a mop-up by the Japanese infantry of any enemy troops that successfully made landfall.
The Imperial Headquarters in Japan upset this plan early on by transferring the 25,000-man 9th Division from Okinawa to Taiwan. These men could have been used to repel the enemy troops that made it ashore during the initial landings. Moreover, an additional 5,400 men of the 6,000-man contingent of the 44th Independent Mixed Brigade were lost when the 6,000-ton transport Toyama Maru was sunk en route from Japan to Okinawa by the American submarine Sturgeon. Only 600 men from the 44th and the Toyama Maru’s crew survived the attack. The Japanese High Command was then forced to reconstitute the 44th Mixed Brigade with the addition of local draftees and other miscellaneous reserve personnel.
The Imperial High Command also promised the Okinawa defenders heavy support from squadrons of kamikaze planes and ships to disrupt the landings. Kamikaze pilots, successfully used in the defense of the Philippines, would crash their aircraft into the decks of the American ships. Small one-man submarines and torpedo boats, some 700 in number and stationed at islands within the Ryukyu chain, would also be employed to attack the incoming Americans. Once the American fleet had been decimated by Japanese air and sea forces, and the newly landed American troops were deprived of the necessary logistical support, the 32nd Army would begin a counterattack against the invaders.
According to the 32nd Army’s senior staff officer in charge of operations, Colonel Hiromichi Yahara, the reduction in available ground troops, such as the 9th Division, required a major revision of the initial plans. Instead of meeting the invaders as they landed on the beaches and defending the airstrips in the beach areas, the Japanese forces elected to dig in on the south end of the island and destroy the invaders as they moved south against the heavily fortified island installations. These static defenses came to be known as the Naha-Shuri-Yonabaru Line, stretching from the island capital, Naha, on the west coast, to Yonabaru, a port city on the island’s east coast.
The Japanese defense plan called for the creation of a series of strongpoints along a number of ridges and escarpments that surrounded the ancient walled city dominated by Shuri Castle. Concentric rings of fire zones permitted the defenders at the strongpoints to protect one another from the advancing Americans. All defensive positions were heavily fortified and contained deep subterranean excavations to protect the troops from enemy bombardment. The Japanese 62nd Division faced the Americans at Shuri. The 24th Division, remnants of the 44th Independent Mixed Brigade, and miscellaneous Japanese naval units backed up the 62nd behind the Shuri Line.
Lieutenant General Mitsuru Ushijima arrived on Okinawa on August 11, 1944, to assume command of the Japanese forces. It was his method of operation to depend on the recommendations of his subordinates in carrying out the mechanics of the island’s defenses, although he took full responsibility for them. This lack of direct involvement in tactical planning was quite common among the senior officers of the Imperial Japanese Army.
Major General Isamu Cho, Ushijima’s chief of staff, practiced no such detachment. Cho had the reputation of being tough, decisive, aggressive, and forceful. He would demonstrate these qualities as the battle for the island proceeded.
Colonel Yahara provided the overall strategic plan for the Imperial Army’s defense of Okinawa. Conservative and pragmatic, he chose to organize the Japanese Army into a defensive posture, ensuring that the Americans would pay the maximum price in their attempts to unseat the island’s defenders. Yahara had to curb the impetuous General Cho, who sought to persuade Ushijima to launch an offensive campaign.
The preparation of the invading American forces would prove to be the most comprehensive in their history. Over 1,600 ships carrying 500,000 soldiers, sailors, and Marines along with their weapons and supplies headed for Okinawa prior to April 1945 from the Philippine Mariana and Caroline Islands as well as the continental United States. The bulk of the attackers had to cross almost 8,000 miles of ocean to arrive at their destination.
Operation Iceberg, as the Okinawan invasion came to be called, lay under the overall direction of Fleet Admiral Chester Nimitz, commander of the Pacific Ocean Area (POA), headquartered in Hawaii. His main striking force for the invasion would be the 5th Fleet’s Task Force 58, commanded by Admiral Raymond Spruance. Aircraft carriers and their support vessels dominated the task force. The tactics for the invasion itself called for two groups: the Covering Force of two fast carrier task groups—one American and one British under Admiral Bruce Fraser—and the Joint Expeditionary Force, which included all of the naval elements and ground troops directly involved in the landings. Vice Admiral Richmond Kelly Turner would be in direct command of the amphibious forces making the landings.
Lieutenant General Simon Bolivar Buckner would command the invading force ashore. Designated as the Tenth Army, it consisted of the XXIV Corps of the U.S. Army, which included the 7th and 96th Infantry Divisions and the III Marine Amphibious Corps, commanded by Maj. Gen. Roy G. Geiger. Geiger’s corps consisted of the 1st and 6th Marine Divisions, with the 2nd Marine Division held in reserve.
Buckner also had the 27th and 77th Infantry Divisions available in reserve. The American general thus commanded a landing force larger than the one employed in the Normandy invasion the previous year. Over 180,000 soldiers and Marines would be going ashore.
The American master plan called for a landing in force at the Hagushi Bay beaches in west-central Okinawa, followed by a drive across the island’s narrow center. This action would be followed by a sweep both north and south from the center. The invaders also planned to seize the vital Yontan and Kadena Airfields close to the initial landing area as quickly as possible.
Prior to the invasion of Okinawa itself, Admiral Turner ordered an American strike force to seize a group of islands, the Keramas, off Okinawa’s southwest coast, as well as a small adjacent group called the Keise Shimas. The Keramas contained a substantial anchorage, which would prove to be an ideal facility for ships, either those waiting to unload off the Okinawan beaches or those that were damaged by the kamikaze attacks during the landings. A bonus for the Americans was the discovery of a large flotilla of suicide motor boats that the Japanese planned to use against the U.S. fleet.