Okinawa is part of Japan and was expected to be defended forcefully by the Japanese Army. Okinawa is sixty miles long and from two to sixteen miles wide. Its topography and irregular terrain facilitated the Japanese defense. There was a pre-invasion population of about 500,000.
Today in WW II: 2 Aug 1939 Albert Einstein writes to Pres. Roosevelt about the potential for a uniquely powerful uranium weapon and indications of German interest in it, the inspiration for the Manhattan Project. More↓
The invasion of Iwo Jima on 19 February 1945 (secured in March) breached the Japanese inner defensive perimeter. To keep up the momentum, the Allies planned to move even closer to the Japanese home islands to capture Okinawa, only 360 miles from Japan and considered part of the Japanese homeland. The Japanese had extensively fortified the island during 1944 and committed 120,000 troops of Japan's 32nd Army to defend it. The Japanese were determined to repel the invasion and they assembled hundreds of aircraft, small boats and manned torpedoes and began emphasizing suicide training.
Preparing for the Invasion of Okinawa
In late March 1945, nearly 1,300 Allied ships converged to participate in Operation Iceberg, the invasion of Okinawa and the Ryukyus Islands, the largest operation of the Pacific war, similar in size to the Normandy invasion of western Europe. Although not known at the time, this tremendous effort would be the final major battle before the surrender of Japan. The Allies committed over one-half million men for the operation including three Marine divisions and four Army infantry divisions. A fifth infantry division waited in New Caledonia in reserve.
The first landing in the Ryukyus took place in the Kerama Islands, fifteen miles from Okinawa, on 26 March 1945. Three other subsidiary landings followed immediately, and by 31 March American forces had secured all the Keramas. On 31 March the Americans landed without opposition on Keise Shima, four small islands eight miles west of the Okinawan capital of Naha. Two artillery battalions were immediately deployed to Keise Shima, with twenty-four 155mm guns to support the attack on Okinawa itself.
Invasion of Okinawa, 1 April 1945
The main landing on Okinawa (L-Day) was on 1 April 1945, Easter Sunday, supported by the heaviest concentration of naval gunfire ever expended to support an amphibious landing. Based on the experience of previous campaigns, the Allies committed the necessary forces to insure that they had complete control of the air and sea before the invasion.
On L-day the Navy and Coast Guard landed 16,000 troops in the first hour on the Hagushi west-facing beaches. By nightfall more than 60,000 were ashore.. By the end of 2 April, elements of the 7th Infantry Division had crossed from the west to the east coast of Okinawa . Elements of the 1st Marine Division reached the eastern shore the following day. cutting the Japanese forces on the island into two groups.
Tenacious Japanese Defense of Okinawa
The largely unopposed landings and quick progress were deceptive. The Japanese developed a deliberate defensive strategy after their experience on Saipan. They did not contest the landings, except for some minor air attacks and light artillery and mortar fire on the beaches. They now planned to focus their defensive strength in the interior, concentrated around strong points in the central and southern parts of the island.
The Japanese 32nd Army built its main defensive positions across the Okinawa isthmus on the "Shuri Line," running from Uchitomari on the west coast to Tsuwa on the east. The rugged terrain in this area hid hilltop pillboxes, caves and bunkers. Because the terrain was hilly and irregular, it provided innumerable short fields of fire, ideal for the Japanese who relied on large numbers of short-range weapons. The tangled, broken ground forced the Americans to fight a thousand small battles hand-to-hand instead of one large battle at a distance where American long-range land, sea, and air firepower would have given them the advantage.
Japanese Counterattacks in the Battle for Okinawa
The invasion of Okinawa was conducted from a huge sea base, in the waters of the Ryukyus with support extending all the way back to the Marianas Islands, 800 miles away. On 6 April, the Japanese began their counterattack against the fleet off the island using suicide planes and manned torpedoes. These Kamikaze attacks sank six ships, heavily damaged seven more and slightly damaged four others, the first of 120 ships sunk or damaged during the campaign. The Japanese also planned to use small, fast boats, loaded with one or two depth charges to attack the fleet, but most of these were captured or destroyed before they could be deployed.
On 6-7 April the increasingly desperate Japanese attempted a surface fleet raid from Kyushu, led by the world's largest battleship Yamato, including a cruiser and eight destroyers. The huge 72,000 ton Yamato and its escorts attempted to attack the invasion fleet, but 300 American carrier planes caught the Japanese at sea. The Yamato, the cruiser and three destroyers were sunk with the loss of about 3,700 men against American losses of only 10 planes and twelve men.
The Campaign to Secure Okinawa
U.S. 6th Marine Division quickly secured the northern half of Okinawa, but American forces were soon bogged down against the Shuri Line defenses. The Japanese fought tenaciously, entrenched in their pillboxes, concrete emplacements, fortified caves, and other ingenious prepared defensive positions. Desperate hand-to-hand fighting was common with thousands of casualties on both sides. Shuri, Okinawa's second largest urban area, cultural center, and ancient royal capital was the major target, but heavily defended in depth and hard to approach by land.
From 12-18 May, the 6th Marine Division fought to capture Sugar Loaf Hill, a 50 foot elevation approximately 300 yards long, strategically anchoring the western end of the Japanese defensive line. Sugar Loaf became a killing ground, as the 6th Marine Division suffered over 2,600 killed or wounded and another 1,300 lost to exhaustion or combat fatigue in seven days of back and forth assaults to take Sugar Loaf summit and move against the flank of the defensive line.
Marines entered Wana Ridge and Wana Draw, east of Sugar Loaf, on 14 May, but were not able to fully subdue the defenders in their maze of fortifications, until after the withdrawal of the Japanese at the end of the month. The Sugar Loaf complex in the west was seized by the 6th Marine Division on 18 May after horrific fighting and Conical Hill on the eastern end of the Shuri Line was captured by the 96th Infantry Division on 21 May. Shuri no longer seemed invincible.
Near the end of May 1945, the campaign to seize Okinawa was two months old. Week after week of costly, exhausting, attrition warfare against the Shuri complex, centered on Shuri Castle in southern Okinawa was finally bearing fruit. Although the Shuri heights had provided superb fields of observed fire covering Naha, its port and the entire five-mile neck of southern Okinawa, Gen. Ushijima, commander of the Japanese 32nd Army, had seen his position erode and had gradually evacuated his troops out of Wana Draw and the Shuri Line during second half of May. When the Marines finally arrived at Shuri Castle on 29 May, they found it only lightly defended.
Gen. Ushijima withdrew to his final command post in a cave near the sea and conducted a fierce, last ditch defense of every yard of southern Okinawa. It took another three weeks, until 20 June, for 7th Infantry Division troops to reach the top of Hill 89, the site of Ushijima's headquarters. The final battle ended with the Harakiri suicide of Ushijima and his Chief of Staff at 0430 hours on 23 June 1945.
Summary of the Battle of Okinawa
Despite their tremendous numerical superiority, it took the Army and Marines almost three months, from 1 April to 23 June 1945, to secure the island. The battle for Okinawa was one of the longest and one of the costliest of the war, claiming over 13,000 American lives and over 57,000 other casualties, including combat exhaustion. The Japanese fanatical attempt to defend the islands cost them an estimated 120,000 dead. About 7,000 Japanese uncharacteristically surrendered at the end. There was much suffering by the Okinawan population -- about 150,000 died in the "Typhoon of Steel" required to overwhelm the Japanese.
Two months later, on 2 September 1945, after the atomic bombings of Hiroshima and Nagasaki in August, Japan surrendered, bringing World War II to a close.
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