Ryukyu Islands
by Jack McKillop

Physical Description & History


     The Ryukyu Islands (Nansei Islands in Japanese) are a group of islands in the western Pacific Ocean about 650-miles (1,046-kilometers) long and stretching southwest from Kyushu Island, Japan to 60-miles (97-kilometers) east of Formosa (now Taiwan). The total land area is 1,850-square-miles (4,791-square-kilometers).
     The islands are composed of three groups north-to-south:

Satsunan Islands consisting of 23 major islands,
Okinawa Islands composed of 11 major islands, and
Sakishima Islands of 15 major islands.

     The temperature is high and equable throughout the year; humidity is excessive and rainfall sometimes averages 120-inches (305-centimeters) a year. Typhoons sweep across the island chain at frequent intervals, causing widespread property damage.
     The Ryukyu Islands are the tops of three submerged mountain arcs. The chain of islands lies within the path of the warm Japan current. Several bays and inlets provide natural harbors and anchorages. Only a few of the islands have lakes, but all the larger ones have numerous streams, but the water is generally unfit for drinking. The soils are varied in character, the richest being found in the mountain valleys of the larger islands. Most of the smaller islands are infertile.
     All larger islands and many of the smaller ones support a heavy cover of vegetation. Plants typical of the temperate zone are found in the northern part of the island group, while those in the south are mostly subtropical. Except for domesticated horses, dogs, pigs, and cattle, the only large animals are the deer and the wild pig. Rats and mice are common and reptiles include at least five species of deadly venomous snakes. Mosquitoes, lice, mites, and other insects abound and among the many species of fish are some dangerous to man.
     The first mention of Ryukyu Islands’ contacts with China date from 605 A. D., when a mission was sent out from China to secure information about the islands. It failed because of the lack .of interpreters. A second mission, dispatched in 610 A.D., demanded submission and tribute from the local ruler. When this was refused, a primitive expedition was sent out in 611, which burned the royal palace and carried off several captives. For several centuries thereafter no further official contact, either diplomatic or military, took place between the Ryukyus and China. The first recorded contact with Japan occurred in 617 A. D., when some natives arrived at the Japanese court with gifts for the empress. The first contact with Europeans evidently took place in 1543 when a Portuguese ship was driven by a storm to the coast of an island. The crew was well treated and in consequence of this visit, the Portuguese soon began to trade extensively with Kyushu Island, Japan. The Dutch, English, and Spaniards followed the Portuguese, but by 1638 all foreign missionaries and all traders except the Dutch were excluded from Japan. For 200 years after 1638 the Ryukyu Islands were even more isolated than Japan but in 1844 political relations with Europeans began with the visit by a French man-of-war which was hospitably received, in marked contrast to its unfriendly reception by the natives of Formosa (now Taiwan).
     From the dawn of history until recent times the economic and cultural relations of the Ryukyus have been closer to China than to Japan, despite the nearer linguistic and racial ties with the latter. On several occasions the rulers of China sought to bring the islands under their political sway as well but not until 1372 did they succeed in compelling the Okinawans to pay tribute to the Chinese court. From this date Chinese customs and ideas began to pour into the island. This period was one of commercial prosperity and cultural advancement which lasted until the end of Japan's war against Korea in 1609, when a Japanese prince dispatched a fleet and an army, and rapidly subdued several islands. The defeated Okinawan king was taken to Japan where he was hospitably treated, flattered, and royally entertained while political agents assumed complete control of foreign affairs and also were able to exert a strong influence in domestic matters.
     Toward the middle of the 19th century the various western powers became increasingly anxious to open trade relations with Japan, and the Ryukyus were stepping stones in that direction. The French managed to develop a certain amount of trade with the Ryukyus, largely in firearms and machinery, although no treaty was in force at the time. In 1853, Captain Matthew Perry, USN, on his way to Japan where he was to break the policy of seclusion, arrived at Naha and established a coaling station there. He forced the Okinawan government to conclude a treaty with the United States guaranteeing good treatment for American vessels. In 1854 the French obtained a similar treaty, and in 1858 the Dutch. With the opening of direct relations with Japan, however, the Ryukyu Islands ceased to be of importance to the western powers and relapsed again into obscurity.
     By 1879 the Islands had been completely incorporated as a part of the Japanese state. The western powers were notified that the Japanese Foreign Office had assumed responsibility for all foreign relations with the Ryukyus; the king was reduced to viceregal rank in the Japanese nobility, was removed to Tokyo and put on a handsome pension, and the tribute to China was stopped although the Chinese did not formally recognize the sovereignty of Japan over the Islands until the close of the Sino-Japanese War in 1895.
     By the terms of the Washington Treaty of 1922, Japan bound herself to build no new fortifications in the Ryukyus, but after 1935 this agreement became null and void.
     The Okinawa Islands, specifically Okinawa and Ie Shima (officially Iejima), and the Naval Activities Ie Shima and Naval Air Bases and Operating Base Okinawa are covered in this article.

Naval Activities on Ie Shima

     Ie Shima (26º43'13"N, 127º47'21"E) is a small oval island located about 3.1-miles (5.0-kilometers) off the west coast of Okinawa. The island is about 5.5-miles (8.9-kilometers) long east-to-west and 2.75-miles (4.43-kilometers) wide (north-to-south). The island is flat-topped and composed principally of limestone. A sharp pinnacle 557-feet (170-meters) rises from the highest flat surface about 1-mile (1.6-kilometers) distant from the northern and eastern coasts. The high portion of the island is surrounded by a low terrace about 130-feet (40-meters) above sea level. The northern coast contains numerous cliffs, while the remaining coasts are flanked by raised beaches a few yards above sea level. The southern and eastern shores have four good beaches from 9-to-35-yards (8-to-32-meters) wide and from 125-to-900-yards (114-to-823-meters) long. A fringing reef 360-to-720-yards (329-to-658-meters) wide, with scattered coral heads and without natural channels, borders the island. Moderate slopes lead inland from the sea coasts, rising about 20-feet (6.1-meters) to a border of evergreen shrubs. Scattered clumps of trees form two distinct lines between the shrubs and the airfields. Interruption of the tree fringe behind the beaches and breaks in the slope offer good exits in addition to the numerous roads and trails leading inland from all beaches. These roads join with the predominantly east-west road net which links all portions of the island.
     In 1940, there were five principal settlements on the island with a population about 6,900. All civilians had been evacuated before the American landing in 1945.
     Temperatures on the island range from 70-to-83-degrees Fahrenheit (21-to-28-degrees Celsius) during the summer months and from 60°-to-68° F (15°-to-20° C). during the winter. The  prevailing winds are from the south to southeast in June and July. Rainfall averages from 80-to-120-inches (120-to-205-centimeters) annually; May, June, and July being the wettest months.
     On the plateau, the Japanese had built three 5,000-foot (1,524-meter) runways. The two westernmost runways, one north-south and the second northeast-southwest, were in the shape of an “X” and the easternmost runway was a single northeast-southwest runway. No obstructions interfered with the approaches to these; aircraft had unlimited expanses of open water over which to gain altitude. With its pinnacle and oval plateau, Ie Shima resembled a huge, immovable aircraft carrier.
     On 16 April 1945, U.S. Army troops landed on Ie Shima to provide a close-in major air base for use against the Japanese home islands. After fierce fighting, the island was declared secure on 21 April. By 30 April the surface of the Japanese runways on Ie Shima had been restored and extensive mine fields removed. By 12 May an all-weather runway was ready, and the following month two all-weather runways with crowded parking for over 450 planes were operational. Between 13 and 19 May, Republic P-47N Thunderbolts of the U.S. Army Air Forces (USAAF) arrived on Ie Shima and flew their first combat mission on 20 May. They were followed by Vought F4U Corsairs of the U.S. Marine Corps on 21 May.
     The original plans had called for two runways on Ie Shima but this was later changed to four parallel runways. The four were named, west to east, A, B, C and D. All four runways could accommodate fighters and Consolidated B-24 Liberators.

        Runway “A” (26º43'48"N, 127º45'27"E) was a new runway that was 6,000-by-100-feet (1,829-by-30-meters) which was to be completed by 10 August 1945.
        Runway “B” (26º43'36"N, 127º45'56"E) was a new runway that was 7,000-by-150-feet (2,134-by-46-meters) which was to be completed by 1 August 1945.
        Runway “C” (26º43'21"N, 127º46'38"E) was the northeast-southeast runway of the westernmost Japanese airfield. When completed on 10 July 1945, the runway was 7,000-by-150-feet (2,134-by-46-meters).
        Runway “D” (26º43'18"N, 127º47'10"E) was the easternmost Japanese airfield. When completed on 1 September 1945, the runway was 6,000-by-100-feet (1,829-by-30-meters). This runway is now Iejima Airport.

All the airfield construction was performed by USAAF aviation engineers.
     Ie Shima became a naval advance base and the four runways were used by the Naval Air Transport Service (NATS). The naval base included 16,700-square-feet (1,551-square-meters) of general storage and space, 7,475-cubic-feet (212-cubic-meters) of cold storage space, and 4,500-square-feet (418-square-meters) of open storage. In addition to 700-feet (213-meters) of wharfage, there were repair shops covering 5,500-square-feet (511-square-meters); hospital, 2,400-square-feet (223-square-meters); and quarters, 67,692-square-feet (6,289-square-meters). The Navy also used two small pontoon piers and had 64 berths 1,000-yards (914-meters) wide for any Navy ship.

Naval Air Bases and Naval Operating Base Okinawa

     Okinawa Island (26º29'58"N, 127º56'49"E) is the largest of the Okinawa Islands and is home to Naha, the capital of Okinawa Prefecture. The island has an area of 463-square-miles (1,201-square-kilometers) and is located about 325-miles (523-kilometers) south-southwest of the Japanese Home Island of Kyushu. Okinawa is a long, narrow island that is 67-miles (108-kilometers) long and varies in width from 2-to-15-miles (3.2-to-24-kilometers). The coastline is irregular, deeply indented with bays and inlets. Wide fringing coral reefs almost completely surround the island and limit access from the sea. North of a narrow isthmus, the land is rugged, with peaks rising to elevations higher than 1,500-feet (457-meters); south of the isthmus the hills do not exceed 700-feet (213-meters). Although broken by steep limestone cliffs and terraces, extensive areas of gently sloping land are found in the southern portion of the island. Land too steep or unproductive to till is covered with a moderate growth of small pines and coarse grass. In the northern hills, vegetation is heavier and approaches the jungle type. The climate is sub-tropical, and although variations in temperature are not great, the extreme humidity makes even these small variations noticeable. Rains are frequent and often torrential, and typhoons of great intensity frequently sweep across the island.
     The civilian population of Okinawa is estimated to be about 300,000 in 1945.
     Units of the U.S. Army and U.S. Marine Corps invaded Okinawa on 1 April 1945; the island was declared “secured” on 21 June. Japanese installations of engineering importance on Okinawa consisted of limited port and harbor improvements, an extensive but narrow road system, four airfields previously operational according to Japanese standards, two airfields on which construction had started, two water supply systems, and miles of stone masonry seawall. Of no benefit to the Americans were two narrow-gauge railroads, the water supply systems, and the caves and tunnels.
     The main logistical task of the operation was the rapid development of air and naval bases in the Ryukyu Islands to support further operations against Japan. The Base Development Plan for Okinawa provided for the construction of eight airfields with 22 runways, two of which were to be operational by 6 April, a seaplane base, an advanced fleet base at Nakagusuku Bay, and the rehabilitation of the port of Naha to accommodate support shipping. Base development responsibilities also included immediate support of the assault by the early construction of tank farms for the bulk storage of fuel and for the improvement of waterfront unloading facilities and of roads. Later a large construction program was planned that included roads, dumps, hospitals, communications facilities, water supply systems, and housing and recreational facilities.
     On 16 May, an agreement was reached between the Army and Navy that the airfields in the Ryukyus were to be developed for 51 air groups, including 29 USAAF Fifth and Seventh Air Force groups which would move forward as soon as facilities were ready; on 4 June 11 runways were committed to the USAAF’s Far East Air Forces (FEAF), six to Boeing B-29 Superfortress groups, and three to Navy and Marine units. This called for construction of airfield facilities to accommodate 4,000 aircraft.
     The B-29s would be assigned to the USAAF’s Eighth Air Force which had been based in the United Kingdom since 1942. Headquarters Eighth Air Force transferred without personnel, equipment and combat elements to Okinawa on 16 July. On 7 Augsut, the aircrews of the first two B-29 bombardment groups had begun to fly into Kadena Airfield.
     To build so many airfields in so short a time required the largest aviation engineering project ever attempted. There were to be some 25-miles (40-kilometers) of paved runways, while the hardstands, taxiways, and service aprons would require a paved area equal to 400-miles (644-kilometers) of a two-lane highway requiring some 5.5 million truckloads of coral and earth to be moved. And there were the usual difficulties: heavy rains at the end of May forced suspension of airfield work until mid-June, while engineer units kept roads open for the Tenth Army; by 22 June, moreover, only 31,400 of the scheduled Army and Navy construction troops had reached Okinawa. The Navy agreed to accelerate the shipment of construction personnel and equipment and at the height of the airfield construction, a total of 95,000 Army aviation engineers and Navy Seabees were on the island.
     The road network, although extensive, was constructed to standards completely inadequate to meet U.S. minimum requirements. Cuts and embankments were narrow, and curves sharp. Native villages, with stone walls and deep gutters pressing the roadway on both sides, gave limited clearance. The best surface consisted of a thin layer of hand-placed coral stones, which failed under Amercian heavy traffic and could not be maintained with U.S. power equipment. Bombardment by U.S. air and surface craft had destroyed many of the bridges and drainage structures of the road network, and the Japanese, as they withdrew, wrecked with demolition charges those that were left.
     Japanese airfields were too short and their construction too light to meet the requirements for operation of American heavier aircraft. Hardstands were small and some were surrounded by diamond-shaped revetments, open at the point. Taxiways and hardstands were elaborately camouflaged -- mock villages with potted trees were used to hide aircraft in dispersal areas at Yontan.
     Great emphasis was placed on establishing airfield facilities at the earliest possible moment. Both Yontan and Kadena airfields had been damaged by the pre-invasion bombardment and were further obstructed with mines and booby traps. Army engineers and Navy Seabees occupied these fields on 3 April and immediately began rehabilitation of the existing runways.
     The Japanese had four operational airfields in the southern part of the island before the American invasion. The four were:

  1. Kadena Airfield (26º21'21"N, 127º46'03"E) had been damaged by the pre-invasion bombardment and was further obstructed with mines and booby traps. Construction troops occupied these fields on 3 April and immediately began rehabilitation of the existing runways; it became serviceable on 6 April and U.S. Marine Vought F4U Corsairs arrived. They were followed by U.S. Army Air Forces (USAAF) Douglas A-26 Invaders in July. Initial efforts were concentrated on clearing runways, repairing bomb craters, and disposing of unexploded bombs and ammunition. The Japanese runway was rebuilt with coral and lengthened to 6,500-by-200-feet (1,981-by-61-meters) and could accommodate fighters and Consolidated B-24 Liberators. A second runway, 7,500-by-200-feet (2,286-by-61-meters) made of asphalt, was built for B-29 Superfortresses and six squadrons of B-29s arrived between 5 and 13 August. A third runway, also asphalt and measuring 7,500-by-200-feet, was under construction and estimated to be completed by 15 September. Kadena Airfield is now Kadena Air Base operated by the U.S. Air Force.
  2. Machinato Airfield (about 26º15'30"N, 127º42'19"E), was captured by the end of April and two 6,000-by-150-foot (1,829-by-46-meter) runways accommodating B-24 Liberators became operational. This base was the home of a USAAF A-26 Invader unit.
  3. Naha Airfield (26º11'55"N, 127º38'41"E), had a 7,000-by-200-foot (2,134-by-61-meter) asphalt runway and was the site of an air depot servicing all USAAF aircraft on the island. Today, this airfield serves as Naha Airport.
  4. Yontan Airfield (26º23'31"N, 127º44'48"E) had also been damaged by bombardments and was also occupied by construction troops on 3 April. One coral runway was ready for fighter operations on 4 April and Marine F4U Corsairs arrived. This runway was later extended to 6,000-by-150-feet (1,829-by-46-meters). At the end of April, construction was started on a new 7,000-by-150-feet (2,134-by-46-meters) coral bomber runway which could accommodate fighters and North American B-25 Mitchells. A second 7,000-by-150-foot runway was under construction when the war ended.

In addition to the four former Japanese airfields above, the U.S. either built or began construction of six additional airfields. The six were 

  1. Awase Airfield (approximately 26°18'48"N, 127°49'01"E) was a coral 5,000-by-150-foot (1,524-by-46-meter) fighter strip for the U.S. Marine Corps. The field was located in a rice paddy area on the east coast of the island, where drainage was poor and the sub-base was a blue clay which became unstable when wet. The nearest sources of coral for fill and surfacing were located 3- and 5-miles (4.8- and 8-kilometers) distant, although a limited supply of finger coral and coral sand was available on the Awase Peninsula. The field was urgently needed as a base for fighter aircraft conducting the air defense of the island, and the desired operational date was set at 1 July. Seabees began construction of Awase on 23 April. Rice paddies were drained; large drainage canals were dug; and tide gates, installed in the sea wall. A bypass for the main supply road was constructed next, and traffic diverted around the field. These preliminary steps had been nearly completed and work was under way on the fills when the torrential rains of late May and early June caused the military to divert all heavy earth-moving equipment to the maintenance of main supply roads. On 30 June, the runway was pronounced ready for initial operation by F4U Corsairs. The airfield was abandoned after the war.
  2. Bolo Airfield (26°26'20"N, 127°43'07"E) consisted of two parallel asphalt 8,500-by-200-foot (2,591-by-61-meter) runways built to accommodate B-29 Superfortresses. Seabees completed the first runway about 1 August and two USAAF squadrons of Curtiss C-46 Commandos were based here. The second runway that was scheduled for completion on 1 October was never completed. This airfield was abandoned after the war.
  3. Chimu Airfield (approximately 26°27'34"N, 127°55'04"E) was built as a fighter and medium bomber base with a 5,000-by-150-foot (1,524-by-45-meter) coral runway. Seabees began work on this airfield for the U.S. Marine Corps on 6 May; the first F4U Corsairs arrived in early July. This airfield was abandoned after the war.
  4. Futenma Airfield (26°16'22"N 127°45'24"E) was built for B-29 Superfortress operations but was not completed before the end of the war. The plan was to build two 7,500-by-200-foot (2,286-by-61-meter) asphalt runways with completion dates in November. With the end of the war, the airfield became a USAAF installation known as Futenma Air Base, and was used as a support airfield for the nearby Kadena Air Base, hosting fighter-interceptor squadrons as part of the air defense of the Ryukyu Islands. The base was transferred to the U.S. Navy on 30 June 1957 and was subsequently developed into a major United States Marine Corps air station.
  5. Motuba Airfield (26°41'09N, 127°53'24"E) was built as a B-24 Liberator base with two 7,000-by-200-foot (2,134-by-61-meter) coral runways that were scheduled for completion in September. Construction had advanced to the point that USAAF P-38 Lightnings were based here in August. The base was abandoned after the war.
  6. Yonabaru Airfield (approximately 26°12'27"N, 127°45'47"E ) was built as a Consolidated PB4Y-2 Privateer base for the U.S. Navy. The runway was planned to be 7,000-by-150-feet (2,134-by46-meters) of Marston Mat. As of 15 August, the airfield became operational, with the completion of 6,500-feet (1,981-meters) of runway. The Navy based at least two squadrons of PB4Y-2s at the base.

     The seaplane base, Naval Air Base Chimu Wan (26°21'16"N, 127°52'7"E), was established in July 1945.  On 14 July, the first of three squadrons equipped with Martin PBM Mariners supported by a seaplane tender arrived. The last wartime operational flights for these squadrons were made from this location on 11 August. The base was disestablished after being destroyed by typhoons in September and October 1945.

  In addition to building airfields, major construction projects completed by the Seabees during the combat period included the Third Amphibious Corps evacuation hospital at Yontan, Special Augmented Hospital 6, a traffic circle near Kadena Field, and pontoon piers at Kuba Saki, Machinato, Awase, and Bisha Gawa. Major construction projects begun by Seabees during that same period included six highways, Special Augmented Hospital 7 and 8, a fuel pier and a pontoon pier at Katchin Hanto, a breakwater at Tengan, an ammunition depot at Chimu Wan, a section base at Katchin Hanto, a minecraft storm refuge at Unten Ko, a receiving station at Kuba Saki, boat pool facilities at Bisha Gawa, a degaussing station at Tsuken Shima, and a joint communications center.

     During the period from 1 July to 31 August, construction troops were able to continue and complete many of the base-development projects begun during the combat period and to begin the construction of all base-development projects which had been delayed because the Japanese prevented occupation of the selected sites. During this period, Seabees completed the Special Augmented Hospitals 3 and 6, Mine Assembly Depot 8, a degaussing range at Tsuken Shima, a minecraft storm refuge at Unten Ko, and a pontoon barge and landing ship, tank (LST) pier at Baten Ko. They also continued to work on the construction of communication facilities, including the erection of a joint communications center, the receiving station at Kuba Saki, naval facilities at Bisha Gawa, the repair base at Baten Ko, the fuel pier at Katchin Hanto, and the breakwater at Tengan.

     An advance base construction depot was started during this period. It included a spare parts depot and an automotive construction equipment overhaul and repair depot. New construction of port facilities included an ammunition pier at Chimu Wan, a pontoon barge pier at Tsuken Shima, a general cargo pier at Katchin Hanto, and two piers for the naval supply depot at Tengan. Large base facilities were started at the supply depot, the naval bases at Buckner Bay and Chimu Wan, and the section base at Katchin Hanto. Other new projects included a naval ammunition depot, Special Augmented Hospital 4, a fleet petroleum storage facility, a tank farm, permanent water systems at Tengan and Baten Ko, a ship repair base at Baten Ko, and docking facilities for aviation repair ships at Awase.

     When the Japanese government formally surrendered on 2 September, naval construction troops were directed to proceed with projects underway. Major projects included the naval operating base at Baten Ko, the Kuba Saki receiving station and staging area (for demobilization of troops), ammunition depot, Fleet Hospital 116, the Katchin Hanto section base, the aviation supply depot, Baten Ko fleet landing, and a fleet recreation area at Tsuken Shima, as well as additions to the naval supply depot at Tengan on Chimu Wan.

     Extensive damage to installations was caused by a severe typhoon, the center of which passed over the southern portion of the island on 9 October 1945. It necessitated the concentration of construction troops for the reconstruction of the fleet post office at Baten Ko, Special Augmented Hospital No. 4, and other facilities required for demobilization.

     By the close of 1945, naval facilities on Okinawa covered 20,000 acres (8,094 hectares), and included 4,180-lineal-feet (1,274-meter) of wharves, 712,000-square-feet (66,147-square-meters) of general covered storage, 11,778,000-square-feet (1,094,212-square-meters) of open storage, 193,000-cubic-feet (5,465-cubic-meters) of cold storage, as well as storage for 8.8 million U.S. gallons (7.34 million Imperial gallons or 33.39 million liters) of aviation gasoline, 30,000 barrels (1.26 million U.S. gallons or 1.05 Imperial gallons or 4.77 million liters) of diesel oil, 50,000 barrels (2.1 million U.S. gallons or 1.75 million Imperial gallons or 7.95 million liters) of fuel oil, 13,000-square-feet (1,208-square-meters) for ammunition. Aviation repair shops covered 324,100-square-feet (30,110-square-meters) and general repairs shops, 91,000-square-feet (8,454-square-meters). Hospital space amounted to 338,000-square-feet (31,401-square-meters), and quarters 4.755-million-square-feet (441,754-square-meters).

     The Battle of Okinawa was a brutal event with horrendous casualties:

 * 142,058 civilian killed by American and Japanese troops or who had committed suicide

* 110,000 Japanese soldiers and sailor were killed and 7,400 captured

* 12,520 American military were killed and 36,631 wounded

      The U.S. Navy sustained 9,781 casualties, 4,907 killed and 4,874 wounded. Because of kamikaze attacks, 28 Allied ships, including 15 amphibious ships and 12 destroyers, were sunk and 368 ships, including 120 amphibious craft, were damaged.

     After the Japanese surrender in 1945, Okinawa was under United States administration for 27 years and the U.S. established numerous military bases on the island. In 1972, the U.S. government returned the islands to Japanese administration.