Volcano Islands
by Jack McKillop

Physical Features

     The Volcano Islands are a group of three Japanese islands south of the Bonin Islands in the western Pacific Ocean. The islands are all active volcanoes lying atop an island arc that stretches south to the Mariana Islands. The three islands, stretching 85-miles (137-kilometers) north-to-south, are:

     The major island is Iwo Jima (24º47' 03"N, 141º19' 31"E) located 765-miles (1,231-kilometers) south of Tokyo and 720-miles (1,159-kilometers) north-northwest of Saipan in the Mariana Islands. The island is about 5-miles (8-kilometer) long in a northeast-southwest direction.  British Captain James Cook's surveying crew in 1776 to 1779 landed on an Iwo Jima beach which is now 131-feet (40-meters) above sea level because of volcanic uplifting. Such uplifting occurs on the island at a varying rate of between 3.9 and 31-inches (99 and 787-millimeters) per year, with an average rate of 8-inches (203-millimeters) per year.
     A plateau about 1-mile (1.6-kilometer) in diameter comprises the central area of the northern half of the island. The surface is irregular, but maximum difference in elevation amounts to only about 50-feet (15-meters). Slopes from the central plateau to the coast have an average grade of about one in ten, but they are rough and irregularly broken by rocky cliffs.
     Iwo Jima is bordered on the north by a rough rocky coast dominated by cliffs, and in the southeast and southwest by beaches, which are composed of coarse to fine sand of volcanic origin. The vegetation on the island is mainly scrubby, except for former shade and palm trees on the north central area which has been badly mauled by gunfire. Most of the vegetation appears to have been imported and bunch grass has been planted to hold the sand in place along the sandy areas above the beaches.
     In 1943 the civilian population of Iwo Jima was estimated at 1,091 most of whom resided at Moto Ya, a settlement in the northeast section of the island. The populace subsisted by growing sugar cane for export, and vegetables for local consumption. Fishing supplemented the local food supply. Considerable quantities of sulphur are present on the island, but not much use seems to have been made of it. At the southwest tip of the island, Suribachi Yama, a volcanic cone, rises abruptly to  545-feet (166-meters). Throughout 1944 there was a massive military buildup on Iwo Jima, in anticipation of a U.S. invasion and in July the civilian population was forcibly evacuated, and no civilians have permanently settled on the island since.
     Average temperatures vary from 64 degrees Fahrenheit (17.8 degrees Celsius) in January and February to 81 degrees Fahrenheit (27.2 degrees Celsius) in August. Rainfall averages around 60-inches (1.5-meters) a year, the wettest months being May and August, while February and March have the least amount of precipitation.
     Gales are rare but occasionally when typhoons pass close by winds are exceptionally strong. Generally the strongest winds prevail in the winter from northwest to west. Fog is rare and low visibilities occur infrequently. Months with lowest visibility are May and October.

History

     The islands were uninhabited until 1889, when the two northern islands were settled by Japanese settlers from the Izu Islands, a group of volcanic islands stretching south and east from the Izu Peninsula of Honshu, Japan. Iwo Jima was annexed by Japan in 1891 on the pretext of lawlessness and lack of recognized government. The population was about 1,100 in 1939, distributed among five populated places on Iwo Jima and two on Kita Iwo Jima.
    
The Volcano Islands in World War II

     U.S. planning for the Central Pacific in 1944 was to capture Guam, Saipan and Tinian in the Mariana Islands (qv) and build airfields on the three islands to accommodate Boeing B-29 Superfortresses in attacks against the Japanese home islands.. The Japanese occupation of Iwo Jima was a problem to the U.S. Army Air Forces (USAAF). First, Iwo Jima is located slightly northwest of the aerial midpoint between Tokyo and Saipan, Iwo Jima's airfields in Japanese hands constituted a serious annoyance to the newly launched long range bombardment of Japan by the USAAF’s Twentieth Air Force from the Mariana Islands. Japanese interceptors from Iwo Jima forced the B-29s to make long detours on their way to the Japanese islands as well as on their return trip to the Mariana Islands. B-29s en route to Japan routinely flew a dogleg-course around the island increasing the already extended distances they were forced to cover. Despite the dogleg, there were no hiding the giant aircraft formations of B-29s from radar surveillance and Iwo Jima gave the home Japanese Islands time to prepare for the bomber stream.
     In addition, the island served as a staging point for Japanese bombers and fighter-bombers, which flew down from their home islands to attack various B-29 bases between October 1944 and January 1945. From two operational airfields on Iwo Jima, Japanese fighters, and other sundry small and medium bombers staged operations to annoy the U.S. bomber force, especially on Saipan Island. For example, in strikes from 2 November 1944 to 2 January 1945, Japanese aircraft destroyed 11 B-29s outright and damaged another 47 seriously on Isley Field, Saipan. Though losing as many as half the about 80 aircraft that staged the raids, the Japanese had hit on a valuable tactic - destroy the bombers before they arrived over Japan!
     Iwo Jima could also provide airfields to base long range USAAF fighters, e.g., North American P-51 Mustangs, to escort the bombers to Japan. These airfields could also serve as emergency fields for crippled bombers and/or those running low on fuel.
     The Japanese had built three airfields, Motoyama Number 1, 2 and 3 or simply, South, Central and North fields, on the central plain of the island. South Field (Motoyama Number 1) had two runways, the north-south runway was 5,025-feet (1,532-meters) and the east-northeast to west-southwest runway was 3,965-feet (1,209-meters) long. Central Field had two runways, the east-northeast to west-southwest runway was 5,225 and the east-west runway was 4,425-feet (1,593-meters and 1,349-meters), built in the form of an X. Motoyama Number 3, with a single  east-northeast to west-southwest runway, never became operational.
     D-Day for the invasion of Iwo Jima by U.S. Marines was 19 February 1945. Three Navy Seabee units were assigned to the Marines during the assault, to act as shore parties and to start work on the airstrips at the earliest possible moment. The island was declared secured on 16 March 1945.
     The basic plan for the development of Iwo into an air base, drawn up in October 1944, contemplated the use where possible of existing Japanese facilities, and although the whole complex was to serve primarily as a B-29 base, the most pressing job was the rehabilitation of some runways for local fighter use. The schedule, a Navy responsibility, was as follows: South Field, one 5,000-foot (1,524-meter) runway was to be rehabilitated for fighter operations by D plus 7; at Central Field, the northeast-southwest runway was to be repaired for fighter use by D plus 10 and the east-west runway extended to a 6,000-foot (1,829-meter) fighter strip by D plus 50; later, by D plus 110, the northeast-southwest runway was to be extended to 8,500-feet (2,591-meters) for B-29s and a second 8,500-foot runway was to be built parallel to the first; and at North Field, one 5,000-foot (1,524-meter) runway was to be ready for fighters by D plus 50. All runways were to be 200 feet (61-meters) wide. Construction was assigned to the Navy Seabees and a USAAF engineer aviation battalion.
     As the airfields were captured, runways were rapidly made serviceable for minimum operations.
     At South Field (24°45' 46"N, 141°18' 13"E), the east-northeast to west-southwest runway was being used by observation planes as early as 26 February (D plus 7), and by 2 March the runway had been graded to 4,000-feet (1,219-meters). On 9 March, this airfield paid its first dividend when a B-29 in distress came in for an emergency landing. Two days later the P-51 Mustangs came up from Saipan, and from then on, South Field was in constant use while construction was continued. On 7 April 1945, P-51s took off from South Field to form the first land-based fighter escort for B-29s on a strike against the Japanese homeland. By July, the runway had been extended to 6,000-by-200-feet (1,829-by-61-meters) and had been surfaced with emulsified asphalt. Also constructed were 7,950-feet (2,423-meters) of taxiways and 258 hardstands. This field could accommodate 100 P-51s and 30 B-24 Liberators. In an emergency, B-29s could land here. This field is now abandoned.
     Although work at Central Field (24°47' 05"N, 141°19' 27"E) was held up by the protracted land battle, on 16 March it too was operational, with the east-northeast to west-southwest runway graded to 5,200-feet (1,585-meters) and the east-west runway to 4,800-feet (1,463-meters). A second runway parallel to the east-northeast to west-southwest runway was also built; both were  built to accommodate B-29s. By 7 July 1945, the first B-29 runway had been paved to 8,500 feet (2,591-meters) and placed in operation. During the day, 102 B-29s, returning from a raid on Japan, landed on the field. Several sub-grade failures occurred in the construction because of ground water and soft spots in the sub-grade. In some places the paving sealed off steam which had been generated below the surface and when the steam condensed, the sub-grade became saturated. By 12 July, the B-29 runway had been completed and paved for a length of 9,800-by-200-feet (2,987-by-61-meters). The parallel runway was eventually lengthened to 9,400-feet (2,865-meters), both with a width of 200-feet (61-meters). The east-west runway built by the Japanese was developed into a fueling strip, 6,000-by-570-feet (1,829-by-174-meters), with 60 fueling outlets. For normal operations, this field could accommodate 120 P-51s and 30 B-24s and 20 B-29s. Today, Central Field is named Iwo Jima Airbase and is operated by the Japanese Self-Defenses Forces.
     Virtually the entire job at North Field (24º47' 43"N, 141º19' 20"E) was new construction in rough terrain which consisted principally of consolidated volcanic ash. The initial portion of the work in preparing the sub-grade for the runway entailed the moving of about 200,000-cubic-yards (152,911-cubic-meters) of rock and volcanic ash. Seabee construction was stopped on 27 April and the project was turned over to a USAAF aviation engineer battalion for completion. By V-J day a runway 6,000-feet (1,829-meters) long, had been graded and was paved to 5,500-feet (1,676-meters); 10,000-feet (3,048-meters) of taxiways had been graded; and 129 fighter hardstands provided. This field could normally accommodate 50 P-51s and 14 B-24s (and eight B-29s in an emergency). North Field was abandoned after the war.
     All facilities on Iwo Jima were constructed to support the air base. Main projects were tank farms, water-distribution system, roads, hospitals, storage areas, and waterfront facilities.
     A temporary tank farm, consisting of four 1,000-barrel (42,000 U.S. gallon or 34,972 Imperial gallon or 158,957 liter) tanks -- two for aviation gasoline, one for motor gasoline, and one for diesel oil -- was ready for operation on 16 March 1945. Dismantling of this farm began when the permanent farms were placed in operation. The permanent tank-farm system consisted of two central farms, called East and West Farms, and small farms at each of the three airfields. Small installations provided 1,000 barrels (42,000 U.S. gallon or 34,972 Imperial gallon or 158,957 liter) of aviation gasoline for South Field; 6,000 barrels (252,000 U.S. gallons or 209,834 Imperial gallons or 953,924 liters) for Central Field; and 6,000 barrels for North Field. The East Tank Farm, for aviation gasoline only, had a capacity of 80,000 barrels (3.36 million U.S. gallons or 2.8 million Imperial gallons or 12.7 million liters). West Farm facilities consisted of 160,000 barrels (6.72 million U.S. gallons or 5.60 million Imperial gallons or 25.4 million liters) for aviation gasoline, 50,000 barrels (2.1 million U.S. gallons or 1.75 Imperial gallons or 7.95 million liters) for motor gasoline, and 20,000 barrels (840,000 U.S. gallons or 699,945 Imperial gallons or 3.18 million liters) for diesel oil.
     All unloading of cargo at Iwo Jima was across the beaches. Berthing was later developed at both eastern and western beaches, the latter proving much more satisfactory. Stevedoring was extremely difficult because of the heavy surf, bad weather, and sand conditions on the beaches. During the assault, Marston mat was extensively used to make possible the landing of wheeled vehicles.
     Harbor development consisted of a breakwater and blockships on the east side of the island and a small boat pool on the west side. A storm wrecked the blockship breakwater, and no further attempt was made to provide seaward protection for ships.
     A project of high priority was the provision of a water-supply system. There are no perennial streams on Iwo Jima and the water table lies at a considerable depth near the center of the island. A fresh-water lens, extending about 9-feet (2.7-meters) above sea-level, had formed, and wells were drilled to secure water from this lens. The Japanese had dug 14 wells, eight of which were used in the development of the water system. In addition, the Japanese had paved catchment-areas which were drained into cisterns excavated in the soft rock. The runoff from the two completed airfields had been stored in masonry and concrete reservoirs, which were repaired by the Seabees and became the basis of the water system. By V-J day, the system was only half finished, with 58 small stills and eight drilled wells.
     Establishment of storage areas for the ordnance, quartermaster, medical, engineering and chemical warfare departments involved the construction of Quonset huts, frame buildings, and open-storage areas, as well as 27,000-cubic-feet (765-cubic-meters) of refrigerated storage space.
     Housing and messing facilities for 37,000 officers and men were set up, in addition to the individual battalion camps. Tents were used for living quarters, and Quonset huts were provided for headquarters and mess halls. Medical facilities were provided at a field hospital, a station hospital and a general hospital with a total capacity of 1,250 beds. There were also 105 beds in Navy dispensaries.
     The first Seabee road construction involved the hacking of a road up Mt. Suribachi to install radar equipment. The Japanese had made no attempt at this construction. After a demolition team had cleared the terrain of mines and booby traps, a bulldozer blazed a trail to the top, and within 12 days, graders, scrapers, and dump trucks had completed the road. To link the various activities on Iwo Jima, 20-miles (32-kilometers) of primary and 40-miles (64-kilometers) of secondary roads were constructed.
     Naval Advance Air Base Iwo Jima was established on the island in 1945 and the facilities were rolled up on 14 August 1946.