By Ivan Toth
The Battle of Iwo Jima (Japanese Iōjima, meaning “sulphur island”) was a major battle in which U.S. Marines landed on and eventually captured the island of Iwo Jima from the Imperial Japanese Army during World War II. The battle lasted from 19 February to 26 March 1945. The American invasion, codenamed Operation Detachment, aimed to capture the entire island, including three airfields controlled by the Japanese, in order to prepare for attacks on the Japanese home islands. The battle, which lasted five weeks, was one of the fiercest and bloodiest engagements fought in the Pacific during World War II.
After heavy losses in manpower, questions were raised regarding the island’s strategic importance. It became apparent that the island was not particularly valuable to the U.S. Army as a launching point for further operations, nor to the U.S. Navy as a naval base; nevertheless, the Navy’s Seabees rebuilt the runways, which were used as emergency landing strips for American B-29 bombers. Japanese defensive positions on the island were strongly fortified, with a dense network of underground bunkers, concealed artillery positions, and 18 kilometres of underground tunnels. The Americans were supported by intense naval gunfire from their warships and maintained air superiority over Iwo Jima from the outset.
The battle is best remembered for the famous photograph by Associated Press (AP) journalist Joe Rosenthal, who captured the raising of the American flag by five Marines and a Navy corpsman atop the 169-meter-high Mount Suribachi. Rosenthal also photographed the second flag-raising on the mountain, which occurred on the fifth day of the 36-day battle. His photograph quickly became an iconic image of the battle, the Pacific War, and the U.S. Marine Corps itself, later becoming widely reproduced and used.
Background of the Battle
After the American capture of the Marshall Islands and devastating U.S. bomber attacks on fortified Japanese positions in the Caroline Islands, Japanese military leaders reassessed the Pacific situation. They concluded that the Americans were likely to move toward the Marianas and the Caroline Islands. To counter such offensives, the Imperial Japanese Army and Navy established inner defensive lines, extending northward toward the Caroline Islands and the Marianas, and toward Japan via the Volcano Islands, as well as westward toward the Marianas through the Carolines, and toward Palau and the Philippines.
In March 1944, the 31st Japanese Army, commanded by General Hideyoshi Obata, was assigned to reinforce and activate garrisons responsible for defending these inner lines. It is worth noting that the Japanese Army was comparable in size to the U.S. Army, the British Army, or the Canadian Expeditionary Force. The Japanese Army fielded numerous divisions, while the Americans had only ten at their peak, with the 4th, 6th, 8th, and 10th divisions deployed in the Pacific; notably, the 10th U.S. Army fought exclusively on Okinawa in spring 1945.
The Invasion Plan
The commander of the Japanese garrison on Chichi Jima was nominally placed in charge of both Army and Navy forces in the Volcano Islands. After the U.S. captured the Marianas, American bombers began daily raids on the Japanese home islands as part of Operation Scavenger. Iwo Jima served as an early-warning station for detecting incoming American bombers, allowing Japanese air defenses to prepare for their arrival.
Following the capture of the Marshall Islands in the battles of Kwajalein and Eniwetok in February 1944, the Japanese Army and Navy sent reinforcements to Iwo Jima: 500 men from the Yokosuka Naval Base and 500 from Chichi Jima arrived during March and April 1944. Additional reinforcements from Chichi Jima and the Japanese home islands increased the island’s garrison to over 5,000 men. The loss of the Marianas in summer 1944 dramatically increased the strategic importance of the Volcano Islands for Japan. Losing these islands would expose the Japanese home islands to American air raids, disrupt war production, and lower civilian morale.
After the Battle of Leyte in the Philippines, the Allies had two months to rest and prepare for further offensive operations before the planned invasion of Okinawa. Iwo Jima was strategically crucial because it hosted a Japanese airbase from which fighter aircraft intercepted U.S. B-29 Superfortress bombers. It also served as a haven and resupply point for Japanese naval forces. The island was used as a launching point for Japanese air attacks on the Marianas from November 1944 through January 1945. Capturing Iwo Jima would resolve these problems for the Allies and provide a staging area for Operation Downfall — the planned invasion of the Japanese home islands. The distance B-29 bombers had to travel would be hypothetically halved, and P-51 Mustang fighters could be based on the island to escort and protect the bombers.
American Intelligence Assessments
U.S. intelligence sources believed that Iwo Jima would fall within a week. Encouraged by these optimistic assessments, American commanders decided to proceed with the invasion, codenamed Operation Detachment. U.S. forces were unaware that the Japanese were preparing a sophisticated and deeply layered defense, significantly departing from their usual strategy of defending the beaches. The effectiveness of the Japanese preparations is evident in the fact that, after the battle, hundreds of tons of Allied bombs and thousands of heavy artillery shells fired at Japanese positions had left many Japanese soldiers almost unharmed and ready to fight, inflicting severe casualties on the Marines.
Japanese Planning and Preparations
By June 1944, General Tadamichi Kuribayashi had been appointed to command the defense of Iwo Jima. Kuribayashi knew Japan could not win the battle, but he hoped to inflict heavy casualties on American forces in order to force the U.S. and its allies — Australia and Britain — to reconsider or even delay the invasion of the Japanese home islands. Drawing inspiration from the Battle of Peleliu, he designed a defense system that broke with standard Japanese doctrine; instead of placing defensive positions on the beaches to confront the invaders directly, he created a strong, mutually supportive defense in depth, using static and heavy weapons such as machine guns and artillery. The tanks under Colonel Takeichi Nishi were repurposed as camouflaged artillery.
Because the tunnel connecting Mount Suribachi with the main Japanese force was never completed, Kuribayashi organized the southern area of the island, including Suribachi, as a semi-independent defensive zone with its main line facing north. Anticipated American naval and air attacks accelerated construction of an intense tunnel network connecting key positions, allowing Japanese troops to retake lost outposts. The network of bunkers and lookout points aided the defense, supported by hundreds of concealed artillery pieces, howitzers, and mines placed across the island. The Japanese also deployed 320 mm howitzers and various types of explosive rockets and bombs.
Despite this, Japanese supplies were insufficient: troops had only 60% of the ammunition required for a divisional counterattack and food, water, and other necessities only for four months. Numerous snipers and camouflaged machine-gun nests were established, and the defense was organized so that every inch of Iwo Jima was subjected to overlapping Japanese fire. Kuribayashi also had a small number of kamikaze pilots at his disposal; during the battle, kamikazes killed 318 U.S. sailors. Against his wishes, Kuribayashi was ordered by his superior, Honshu, to remove some of the beach defenses — the only parts destroyed during the pre-invasion bombardment.
American Preparations
Beginning on 15 June 1944, the U.S. Navy and Air Force carried out daily bombardments of Iwo Jima, making it the longest and most intense bombardment in the Pacific War.
The bombardment combined heavy naval gunfire and aerial bombing and lasted nine months. On 17 June, the destroyer escort USS Blessman deployed Underwater Demolition Team 15 (UDT-15) toward Blue Beach for reconnaissance; one diver was killed by Japanese rifle fire. The next evening, on 18 June, a Japanese bomber struck USS Blessman, killing 40 sailors, including 15 UDT men. Unaware of Kuribayashi’s tunnel network, many Americans believed the prolonged bombardment had destroyed most of the Japanese garrison.
Major General Harry Schmidt, commander of the Marine landing forces, requested an intense 10-day bombardment prior to the mid-February amphibious assault. The request was denied by Rear Admiral William H. P. Blandy, commander of the amphibious support force (Task Force 52), who believed his ships would not have enough time to resupply ammunition before the landing. Schmidt then requested nine days. Blandy again refused and approved only three days. This decision angered the Marines; after the war, Lieutenant General Holland M. Smith, commander of the expeditionary troops (Task Force 56), later lamented that “the lack of naval gunfire support cost Marine lives throughout the campaign.”
Each battleship was assigned an area to bombard, and combined fire from all ships covered the entire island. Each vessel fired for about six hours before temporarily ceasing fire. Poor weather three days before the landing created uncertainty about the bombardment’s effectiveness. Two days before D-Day, the preparedness of Japanese gun positions became clear: the heavy cruiser USS Pensacola suffered six hits from coastal batteries, killing 17 sailors. Later, a boat of 12 men attempting to reach a demolition team landing point was hit by Japanese artillery and forced to withdraw. While rescuing the damaged boat, the destroyer USS Leutze was hit, killing seven sailors.
The day before the landing, naval gunfire was hindered by rain and clouds. Schmidt later noted that the Marines received “only 13 hours of gunfire support during 34 hours of daylight.” The limited bombardment had questionable effectiveness against the deeply entrenched Japanese; however, many bunkers and caves were destroyed, achieving limited success.
