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.
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.
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.