In February 1944, after the U.S. military recaptured the Marshall Islands and launched a devastating air strike on Chuuk in the Caroline Islands in January 1944, the Japanese base camp began to reassess the situation. In order to resist the actions of the American army, the Japanese army established a circular defense ring "absolute defense circle", north and south

The Caroline Islands to the Mariana Islands are one of the island defenses, and the two islands are Iwo Jima to the north, followed by the Japanese mainland. In March 1944, the Japanese Army's 31st Army, commanded by Lieutenant General Hidera Obata, moved into this line. In February 1944, the U.S. military recaptured Guam, and on December 20 of the same year, it landed on Leyte Island in the Philippines. In the ensuing Battle of Leyte Gulf, the U.S. forces basically wiped out the main force of the Imperial Japanese Navy. As a result, the U.S. military canceled its original plan of landing on Luzon or Taiwan at the end of February and early March 1945, and instead directly attacked Okinawa and the Japanese mainland after seizing Iwo Jima.

The air and sea supremacy was basically lost, the distance was relatively long, the whip was beyond the reach, and the cost of support was too great, so Japan's strategy of shrinking inward and fighting a bloody battle with the US military in the mainland or nearby areas was correct. During the Korean War, Ridgway replaced MacArthur in commanding the coalition forces to adopt a similar strategy, allowing the volunteers to stride into depth and increase the difficulty of supply along the long supply lines.

A significant part of the participating forces were supporting the landing operation on Luzon, and the Battle of Iwo Jima had to wait until March 1944, after the end of the Battle of Luzon, and because of the slow progress of the Luzon Campaign, the end date was postponed from the planned February 20, 1944 to March 9, 1944, and Nimitz postponed the operation on Iwo Jima until mid-March 1944. At the beginning of October 1944, the staff officers of the U.S. Pacific Fleet Command formulated a plan to attack Iwo Jima, and the ground force participating in the operation was the 5th Amphibious Army, under the jurisdiction of the 3rd, 4th, and 5th Marine Divisions, a total of about 60,000 people, commanded by Vice Admiral Holland Smith; landing formations and support formations, commanded by Lieutenant General Kelly Turner; Task Force 58, commanded by Vice Admiral Mitchell, was responsible for air and sea cover; All participating landing ships were about 500 ships, about 400 warships, and about 2,000 aircraft, under the unified command of Admiral Spruance, commander of the Fifth Fleet.

Before 1944, the Japanese army only used Iwo Jima as an air relay base in the central and southern Pacific Ocean, and only deployed more than 1,500 naval garrisons and 20 aircraft. After the loss of the Mariana Islands in 1944, the importance of Iwo Jima became increasingly apparent, and the Japanese army began to vigorously strengthen its defenses, sending more than 4,000 army troops to the island in late March 1944; In May, the army units on Iwo Jima were reorganized into the 109th Division, with Lieutenant General Tadamichi Kuribayashi as the division commander, and equipped with 120 and 155 mm shore guns, 100 mm anti-aircraft guns, and twin 25-mm anti-aircraft guns. In July, the Japanese moved the Navy's 27th Air Force to the island, withdrew all non-combatants from Iwo Jima, built underground fortifications, concentrated the main fire at the foot of the mountain, and covered the beachhead. The 5,000 people transferred from Chichijima and the 2,700 people evacuated from Saipan were concentrated on Iwo Jima, and by August, the number had reached 12,700. Later, 1,233 naval sappers came to build fortifications. On August 10, 2,216 Navy arrived.

At the same time, the Japanese army transferred weapons to Iwo Jima, and although many of the ships were sunk by the U.S. forces, by the end of 1944, the Japanese still managed to deliver many weapons to Iwo Jima, including 361 75 mm (or larger) guns, 12 320 mm mortars, 65 150 mm medium mortars and 81 mm light mortars, 33 80 mm naval guns (

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s), 94 anti-aircraft guns of 75 mm caliber (or greater), 69 anti-tank guns of 37 mm and 47 mm caliber, 200 anti-aircraft machine guns of 20-25 mm caliber, 70 rocket launchers, with a range of 90 kg from 2-3 km to 250 kg with a range of more than 7 km.

26 tanks and 28 soldiers of the 600th Tank Wing stationed in Busan, North Korea, headed for Iwo Jima, and although they were attacked by the American submarine USS Cobia (SS-245) on the way, 22 tanks still arrived, placed at strategic points, half-buried in the earth to prevent air raids.

Despite being intercepted by American ships, the Japanese continued to deliver to the island

The Japanese army on the island has about 15,000 troops, about 7,000 navy, a total of about 23,000 people, more than 30 aircraft, and enough food reserves to last for two and a half months

Brandish. The Japanese army built an airfield in the central highlands and Wonsan area of the island, called the Kurdo airfield and the Wonsan airfield respectively, also called the No. 1 airfield and the No. 2 airfield, and built a third airfield north of the No. 2 airfield. Because the US military quickly captured the Mariana Islands, the personnel, equipment, and materials originally planned to be transported to the Mariana Islands were diverted to the nearest Iwo Jima, and although the US military organized planes and submarines to attack with all their might in an attempt to cut off the reinforcements and supplies of Iwo Jima, the Japanese army used Chichijima as a transit point and adopted the method of small boat barge, so the blockade effect of the US military was not ideal.

Because the main force of the Japanese navy and air force suffered a devastating blow in the Philippine Campaign, it was no longer able to provide sea and air support for Iwo Jima, and the anti-landing operation on Iwo Jima had to be carried out with almost no naval and air support. Kuribayashi, an outstanding professional soldier who served as commander of the Emperor's Guard, realized that it would be difficult to achieve a beachhead operation in the face of the absolute superiority of the American army in the sea and air, and advocated a defense in depth by relying on strong fortifications in the favorable terrain of the mountains of Oribayama and Motoyama. The local volcanic ash and cement mixture made very good concrete, and the Japanese army used it to build many very strong underground fortifications, each of which had many exits to prevent people from being besieged, and the large bunkers could even hold 300 to 400 people. The Japanese were also preparing to build a 27,000-meter underground passage connecting all the underground fortifications, and the 18,000-meter had been completed by the time the American troops landed. However, the naval garrison still insisted on annihilating the enemy at the beachhead, and in the end Kuribayashi made a compromise plan, with defense in depth as the mainstay, supplemented by the defense of the beachhead, and the naval garrison building along the beach

Prepare launch points and solid support points for forward defense; The main force of the army was concentrated in the area of Oribasan and Wonsan, and the defense in depth was carried out.

Kuribayashi Tadamichi was determined to build Iwo Jima into a strong fortress, with Mt. Oriba as the core position, two airfields as the main defense area, and a defensive position with permanent launch points and solid support points as the backbone on the east and west beaches suitable for landing. Most of the artillery positions were also built semi-underground, which, despite the sacrifice of the firing range, greatly improved the ability to survive heavy bombardment. The artillery and communication networks were well protected, and the mountain was almost hollowed out, with nine layers of tunnels built! In view of the operational characteristics of the US military, Kuribayashi has planted a large number of ** in the front line of the beach, machine guns, mortars, and anti-tank guns constitute a dense fire network, and the configuration of all weapons and firing targets have been accurately calculated, which can not only conceal themselves, but also kill and injure the US troops to the greatest extent. The disadvantage is that the tunnel fortifications that were originally planned to be built in the Wonsan area are 28 kilometers long, but due to lack of time, only 70% of them were completed when the US military launched an attack, about 18 kilometers, and there was no tunnel connection between Oribasan and Wonsan.

Kuribayashi changed the Japanese army's desperate tactics in the early days of the war, and after drawing on the example of the Japanese army's anti-landing war on Saipan that lost 30,000 men in three days, he advocated the adoption of non-resistance tactics against the US army's beach grabbing. It was not until the vanguard of the US army entered the land 500 meters that it launched a counterattack, using concealed fortifications to kill and injure a large number of US forces at close range. Tactics such as close-range shooting, mobile defense, and ambush were stipulated, and suicide charges were strictly prohibited, and every soldier was called upon to kill at least ten American soldiers. Kuribayashi's painstaking management did cause great difficulties for the US military, making the Battle of Iwo Jima the most brutal and arduous amphibious landing campaign in the Pacific

From August 10, 1944, U.S. Air Forces stationed on Saipan began air raids on the Ogasawara Islands, focusing on the airfield on Iwo Jima and the port facilities on Chichijima, a transit point for the replenishment of Iwo Jima. From August to October, there were 48 bombings, about 4,000 tons of bombs, but with little success.

On November 24, 1944, the U.S. military on Saipan dispatched B-29 Super Fortress bombers to bomb the Japanese mainland for the first time, which caused great fear among the Japanese army, and immediately responded, and three days later, on November 27, 1944, the Japanese army on Iwo Jima dispatched two planes to attack the U.S. B-29 air base on Saipan, destroying one B-29 and damaging eleven planes.

In the days that followed, the Japanese forces on Iwo Jima organized several air raids on the US military air base on Saipan.

Even if the Yamato, the world's largest battleship, is left under the cover of Japan's land-based air force, in front of the US aircraft carrier-based aircraft, it is just a relatively sumptuous dish that will be sent to the bottom of the ocean with a few dozen aerial bombs in front of the US aircraft carrier-based aircraft.

On March 26, the U.S. forces completely defeated the Japanese army, and Kuribayashi Tadamichi was wounded and committed suicide by caesarean section. The Battle of Iwo Jima ended with more than 20,000 U.S. casualties. The Battle of Iwo Jima was the only battle in the Pacific theater in which American casualties surpassed that of Japan, and it was also one of the most brutal. Although the U.S. forces won, the U.S. forces paid great casualties in order to capture this small island, and because the Japanese army adopted new tactics and made full use of the advantages of the terrain, the U.S. troops had to pay heavy casualties every time they pushed forward.