The Battle of Iwo Jima (硫黄島の戦い, Iōtō no Tatakai,or Iōjima no Tatakai; 19 February – 26 March 1945) was a major battle in which the United States Marine Corps (USMC), United States Navy (USN), and United States Army (USA) landed on and eventually captured the island of Iwo Jima from the Imperial Japanese Army (IJA) during World War II. The American invasion, designated Operation Detachment, had the goal of capturing the island with its two airfields: South Field and Central Field.
The Japanese Army positions on the island were heavily fortified, with a dense network of bunkers, hidden artillery positions, and 18 km (11 mi) of tunnels. American ground forces were supported by extensive naval artillery, and enjoyed complete air supremacy provided by US Navy, Army, and Marine Corps aviators throughout. The five-week battle saw some of the fiercest and bloodiest fighting of the Pacific War.
Unique among Pacific War battles involving amphibious island landings, total American casualties exceeded those of the Japanese, with a ratio of three American casualties for every two Japanese. Of the 21,000 Japanese soldiers on Iwo Jima at the beginning of the battle, only 216 were taken prisoner, some only captured because they had been knocked unconscious or otherwise disabled. Most Japanese were killed in action, but 3,000 or more continued to resist within various cave systems on the island after most major fighting ended, until they were hunted down and killed by the US Army, with some eventually surrendering.
The invasion of Iwo Jima was controversial, with retired Chief of Naval Operations William V. Pratt stating that the island was useless to the Army as a staging base and useless to the Navy as a fleet base. The island's airfield did support P-51 Mustang long-range escort fighters to protect B-29 Superfortress bombers en route to Japan, and also for emergency landings of B-29s, although these were of limited value late in the war. The Japanese continued to maintain early-warning radar capabilities on the island of Rota, which was never invaded by American forces. Experiences with previous Pacific island battles suggested that the island would be well-defended and that seizing it would result in significant casualties. Lessons learned on Iwo Jima served as guidelines for American forces in the Battle of Okinawa two months later and the planned invasion of the Japanese homeland.
Joe Rosenthal's Associated Press photograph of the raising of the U.S. flag at the summit of the 169 m (554 ft) Mount Suribachi by six Marines became a famous image of the battle and the American war in the Pacific.
Background
After the American capture of the Marshall Islands and the air attacks against the Japanese fortress island of Truk Atoll in the Carolines in January 1944, Japanese military leaders reevaluated their strategic position. All indications pointed to an American drive toward the Mariana Islands and the Carolines. To counter such an offensive, the IJA and the Imperial Japanese Navy (IJN) established an inner line of defenses extending generally northward from the Carolines to the Marianas, from there to Japan via the Volcano Islands, and westward from the Marianas via the Carolines and the Palau Islands to the Philippines.
In March 1944, the Japanese 31st Army, commanded by General Hideyoshi Obata, was activated to garrison this inner line. (Note that an army-sized unit in Imperial Japanese military doctrine was about the size of an American, British Army, or Canadian Army corps.)
The commander of the Japanese garrison on Chichi Jima was placed nominally in command of IJA and IJN units in the Volcano Islands. After the American conquest of the Marianas, daily bomber raids from the Marianas began to strike mainland Japan in Operation Scavenger. Iwo Jima served as an early warning station that radioed reports of incoming bombers back to the home islands, allowing Japanese air defenses to prepare for the arrival of American bombers.
After the U.S. seized bases in the Marshall Islands in the battles of Kwajalein and Eniwetok in February 1944, Japanese reinforcements were sent to Iwo Jima: 500 men from the naval base at Yokosuka and 500 from Chichi Jima reached Iwo Jima during March and April 1944. At the same time, with reinforcements arriving from Chichi Jima and the home islands, the army garrison on Iwo Jima reached a strength of more than 5,000 men. The loss of the Marianas during the summer of 1944 greatly increased the importance of the Volcano Islands for the Japanese, who were concerned that the loss of those islands would further facilitate American air raids against the home islands, disrupt war manufacturing, and severely damage civilian morale.
The final Japanese plans for the defense of the Volcano Islands were hamstrung by several factors:
- The Combined Fleet had lost almost all of its striking power during naval engagements in the latter half of 1944, and could not interdict American landings.
- Aircraft losses in 1944 had been so severe that even if war production was not affected by American air attacks, the combined Japanese air strength was not expected to increase to 3,000 warplanes until March or April 1945.
- Those aircraft could not be used from bases in the home islands to support the defense of Iwo Jima because their range was not more than 900 km (560 mi).
- Available warplanes had to be hoarded to defend Taiwan and the home islands.
- There was a serious shortage of properly trained and experienced pilots because many pilots and aircrews died in battles over the Solomon Islands in 1942 and the Battle of the Philippine Sea in mid-1944.
In a postwar study, Japanese staff officers described the strategy used in the defense of Iwo Jima:
In the light of the above situation, seeing that it was impossible to conduct our air, sea, and ground operations on Iwo Island [Jima] toward ultimate victory, it was decided that to gain time necessary for the preparation of the Homeland defense, our forces should rely solely upon the established defensive equipment in that area, checking the enemy by delaying tactics. Even the suicidal attacks by small groups of our Army and Navy airplanes, the surprise attacks by our submarines, and the actions of parachute units, although effective, could be regarded only as a strategical ruse on our part. It was a most depressing thought that we had no available means left for the exploitation of the strategical opportunities which might from time to time occur in the course of these operations.
— Japanese Monograph No. 48
After the Battle of Leyte in the Philippines, the Allies were left with a two-month lull in their offensive operations before the planned invasion of Okinawa. Iwo Jima was considered strategically important since it provided an air base for Japanese fighter planes to intercept long-range B-29 Superfortress bombers flying to strike targets in Japan. In addition, it was used by the Japanese to stage intermittent air attacks on the Mariana Islands from November 1944 to January 1945. The capture of Iwo Jima would eliminate those problems. The island's airfield would also support P-51 Mustang fighters, which could escort and protect bombers en route to Japan.
American intelligence sources were confident that Iwo Jima would fall in one week. In light of optimistic intelligence reports, the decision was made to invade Iwo Jima, and the operation was codenamed Operation Detachment.
Planning and preparation
Japanese preparations
In June 1944, Lieutenant General Tadamichi Kuribayashi was assigned to command the defense of Iwo Jima. Kuribayashi knew that if the Americans decided to land on Iwo Jima, his garrison could not win the battle, but he hoped to inflict massive casualties on the American forces so that the United States, and its Australian and British allies, might reconsider carrying out an invasion of the Japanese home islands.
Drawing inspiration from Japanese defensive tactics used in the Battle of Peleliu, Kuribayashi designed a defensive strategy that broke with traditional Japanese military doctrine. Rather than establishing defenses on the beach to contest the landings directly, he opted for defenses in depth. Kuribayashi's troops constructed a complex system of mutually-supporting fortifications, often linked by a vast tunnel system, equipped with heavy machine guns and artillery. Takeichi Nishi's armored tanks were camouflaged and used as static artillery positions. Because the tunnel linking Mount Suribachi to the rest of the island was never completed, Kuribayashi organized the southern area of the island in and around the mountain as a semi-independent sector, with his main defensive zone built up in the north. The expected American naval and air bombardment prompted the creation of an extensive network of tunnels connecting otherwise disparate fighting positions, so that a pillbox that had been cleared could be later reoccupied. This network of bunkers and pillboxes was designed for protracted resistance. For instance, the Nanpo Bunker (Southern Area Islands Naval Air HQ) east of Airfield Number 2, had enough food, water, and ammunition for the Japanese to hold out for three months. The bunker was 90 feet underground with tunnels running in various directions. Approximately five hundred 55-gallon drums filled with water, kerosene, and fuel oil for generators were stored inside the complex. Gasoline-powered generators allowed for radios and lighting to be operated underground.
By the time the Americans invaded on 19 February 1945, 18 km (11 mi) of a planned 27 km (17 mi) of tunnels had been dug. Besides the Nanpo Bunker, there were numerous other command centers and barracks 75 feet below ground. Tunnels allowed for troops to move undetected between defensive positions. Hundreds of hidden artillery and mortar positions were placed all over the island, and many areas extensively mined. Among the Japanese weapons were 320 mm spigot mortars and a variety of explosive rockets. Nonetheless, the Japanese supply situation was inadequate. Troops were supplied 60% of the ammunition normally considered sufficient for single engagement by one division, and food for no more than four months.
Numerous Japanese sniper nests and camouflaged machine gun positions were set up. Kuribayashi engineered the defenses so that every part of Iwo Jima was subject to Japanese defensive fire. He also received a handful of kamikaze pilots to use against the enemy fleet; their attacks during the battle killed 318 American sailors. However, against his wishes, Kuribayashi's superiors on Honshu ordered him to erect some beach defenses.
Starting on 15 June 1944, the U.S. Navy and the U.S. Army Air Forces began shore bombardment and air raids against Iwo Jima, which would become the longest and most intense preliminary bombardments in the Pacific Theater. They consisted of a combination of naval artillery attacks and aerial bombings, which would last for nine months. Unaware of Kuribayashi's tunnel defense system, some American planners assumed that most of the Japanese garrison had been killed by the constant bombing raids.
On 17 February 1945 the destroyer escort USS Blessman deployed Underwater Demolition Team 15 (UDT-15) onto Iwo Jima's Blue Beach for reconnaissance. They were spotted by Japanese infantry and fired upon, killing one American diver. On the evening of 18 February, Blessman was hit with a bomb by Japanese aircraft, killing 40 sailors, including 15 members of the UDT.
Pre-landing bombardment
Major General Harry Schmidt, commander of the Marine landing force, requested a 10-day heavy bombardment of the island immediately preceding his planned amphibious assault. However, Rear Admiral William H. P. Blandy, commander of the Amphibious Support Force (Task Force 52), believed that such a bombardment would not allow him time to replenish his ships' ammunition before the landings; he thus refused Schmidt's request. Schmidt then asked for nine days of shelling; Blandy again refused and insisted upon a three-day bombardment. This decision was resented among the Marines in the landing force. After the war, Lieutenant General Holland M. "Howlin' Mad" Smith, commander of the Expeditionary Troops (Task Force 56, which consisted of Schmidt's Fifth Amphibious Corps), bitterly complained that a frequent lack of supporting naval gunfire had cost Marine lives throughout the Allied island-hopping campaign.
Each heavy warship was assigned an area on Iwo Jima to saturate with shells, ultimately covering the entire island. Each warship fired for approximately six hours before stopping for a certain amount of time. Poor weather on D-3 (three days before the landings) led to uncertain results for that day's bombardment. On D-2, the time and care that the Japanese had taken in preparing their artillery positions became clear. When heavy cruiser USS Pensacola got within range of Japanese shore batteries, the ship was quickly hit six times and suffered 17 dead. Later, 12 small craft attempting to land a UDT were all struck by Japanese fire and quickly retired. While aiding these vessels, the destroyer USS Leutze was also hit and suffered seven dead. On D-1, Blandy's gunners were once again hampered by rain and clouds. Schmidt summed up his feelings by stating, "We only got about 13 hours worth of fire support during the 34 hours of available daylight."
The limited bombardment had a questionable impact on the enemy since the Japanese were heavily dug-in and well fortified. The craters left behind by the barrage also provided additional cover for the defenders, while hampering the attackers' advance. Despite this, many bunkers and caves were destroyed during the bombardment. The Japanese had been preparing for this battle since March 1944, which gave them a significant advantage. By the time of the landing, about 450 American ships were located off Iwo Jima, and the battle ultimately involved about 60,000 U.S. Marines and several thousand U.S. Navy Seabees.
Opposing forces
American