INVASION OF IWO JIMA: OPERATION DETACHMENT
Location: Iwo Jima
§ Iwo Jima, claimed by Japan in 1861, was regarded as a part of the sacred homeland and therefore had to be defended to the death for Japan’s honour.
§ Volcanic 5mi by 2mi island.
§ 750miles from Japan, and half the distance between the Marianas and central Japan.
§ Mt. Suribachi (546 feet) located at the southern tip; three airfields located north.
Timeline
§ Aug 1944: Preliminary air bombings begin over the Volcano and Bonin Islands.
§ Nov: Preliminary naval bombing by the US begins.
§ Dec 8: US army begins bombing of Iwo Jima for 73 days straight. 800 tons of bombs were dropped on December 8 alone.
§ Feb 12-17: Air raids on Japanese Home Island begin.
§ Feb 15 1945: Preliminary air raids end on Volcano and Bonin Islands end.
§ Feb 19: First landing took place, 40 000 men were on the beaches by nightfall.
§ Feb 23: US flag was raised on Mount Suribachi.
§ Feb 24: Marines took the main airfield on Iwo Jima.
§ Mar 8: P-51s began escort operations from Iwo to Japan.
§ Mar 16: Organized resistance from Japanese ended.
§ Mar 26: US secured complete control of Iwo Jima.
Lt. Gen. Kuribayashi Tadamichi, General of the 109th Division, Japanese Imperial Army
§ Lieutenant General Harry Schmidt of the US Army said “Kuribayashi was one of the most resolute and professionally able soldiers of the IJA, a master of defensive tactics. He had the troops, the opportunity for preparation, and above all, the terrain, which would enable him to complete a defense plan of the most iron-clad character, and this he achieved. Realizing in advance, that he could not prevent a landing by Marines in superior force, he prepared to accept our landing and conserve his strength for a desperate battle on shore.”
§ Kuribayashi said every Japanese soldier “will resist until the end, making his position his tomb.”
Admiral Chester Nimitz, Commander-in-Chief, US Pacific Fleet
§ Promoted to Commander-in-Chief of the US Pacific Fleet after the attack on Pearl Harbor.
§ In the US Navy’s two-pronged assault against the Japanese, Nimitz led the advance through the Central Pacific.
§ Prior to Operation Detachment, Nimitz’s forces took the Gilbert Islands in 1943, the Marshall Islands in February 1944, and began landing in the Marianas in June 1944, capturing Leyte and Luzon.
§ Nimitz was responsible for organizing the attack on Iwo Jima.
§ Admiral Nimitz said that “Among the Americans who served on Iwo Island, uncommon valour was a common virtue.”
Japanese tactics
1. General Kuribayaski understood that a land invasion from the Marines was inevitable.
a. He took defensive precautions by preparing concrete and iron underground reinforcement as deep as 30 feet. By the beginning of 1945, a subterranean network of hospitals, bunkers, and command posts connected by eighteen miles of tunnels was complete.
b. 900 pillboxes were built per 1000 sq. yards. Small ones were approximately 6 x 6 x 6; larger ones were of variable size.
2. Kuribayashi understood that standard tactics would be ineffective against enormous US firepower. Therefore his men applied the 'banzai charge', a suicidal infantry attack.
3. Kuribayaski waited one hour after the invasion began, at which point over 13 000 Americans were landed, before ordering his men to fire.
a. This time allowed the beaches to become packed and the terrain to take its toll on American troops. Volcanic sand clogged weapons and, coupled with explosions, often caused temporary blindness. Digging fox holes in the dense sand was impossible.
b. “The Marines were virtually elbow to elbow and without cover.” Thompson. Empires on the Pacific, 2001.
4. General Kuribayaski had the advantage of height and clear visibility from the peak of Mount Suribachi. “Spotters at the peak directed fire with horrific accuracy. The defenders could detect the Marines’ every move.” Thompson. Empires on the Pacific, 2001.
a. On February 21, the Japanese Air Force sent 50 planes to attack the invasion fleet. Kamikaze raids hit five vessels, including two carriers. The USS Bismarck capsized.
US tactics
1. Preliminary bombing by carrier planes and land-based aircraft (e.g. B-29s) as well as surface ships started in August 1944 over the Volcano and Bonin Islands. By February 15 1945, 7 300 tons of bombs were dropped on Iwo. Airfields were the main target, but shipping was attacked also.
a. Saipan-based 7th Army Air Force B-24s launched 10 raids in August, 22 in September, and 16 in October.
b. On December 8, 62 B-29s and 102 B-24s dropped 814 tons of bombs on airfields in Iwo Jima. Air raids occurred for 73 days straight hereafter.
c. Between February 12-7, U.S. carriers bombed the Japanese mainland. Targets included manufacturing plants, aviation facilities, and shipping. The US wanted to secure aerial superiority during the invasion.
i. Admiral Marc Mitscher’s Task Force 58 bombed the coast of Japan while carrier aircrafts struck airfields in the Tokyo area. This immobilized kamikaze bases that could he used against the fleets approaching Iwo Jima..
2. First, Mount Suribachi would be taken over in the south. The attack on Mount Suribachi was described by one officer as "A frontal assault: surround the base, locate a route up, then climb it!" Thompson. Empires on the Pacific, 2001.
3. Second, the northern airfields of the island were targeted. The infantry’s push forward was aided by Sherman “zippo” tanks, as well as low air support from Hellcats and P-51 Mustangs.
4. Grenades and flamethrowers were most effective against the Japanese subterranean and pillbox fortifications. Hand-to-hand encounters employed the bayonet.
1. Mitsubishi A6M Zero planes (“Zekes”) were used for kamikaze missions. They became outdated by 1944, but retained their high manoeuvrability. They successfully damaged the USS Saratoga and capsized the USS Bismarck.
2. Nakajima B5N torpedo bombers (“Kates”), obsolete since 1941, were available against the US invasion fleet.
3. Four submarines, the RO-43, 1-44, 1-368 and 1-370, armed with 14 kaiten torpedoes constituted the Japanese naval force. The RO-43 was able to damage one US destroyer with conventional torpedoes.
a. Due to US anti-submarine warfare tactics, kaiten attacks were ineffective.
US Technology
1. Heavy bombers including the B-24 Liberator and B-29 Superfortress were primary aircrafts for air raids. The B-29 could fly 32 000 feet, higher than Japanese defensive planes.
2. The F6F Hellcats were used significantly during summer air raids. They were responsible for destroying 70 of 80 Japanese Zekes. Corsairs and Hellcats were also used prior to the February 19 landing to shoot down defensive pillbox fortifications which covered the beaches.
3. The Sherman M4A3R3 “Zippo” tank was equipped with flamethrowers and effective in clearing Japanese positions.
4. P-51 Mustangs, which were incredibly long-ranged, were used to give air support to B-29s during air raids.
5. Anti-submarine warfare technology such as RADAR was extremely effective in detecting Japanese submarines.
Size of Japanese forces
1. Iwo Jima was defended by approximately 24 000 Imperial Army and Navy troops, led by Lieutenant General Kuribayashi Tadamichi.
2. Mount Suribachi was a self-contained fortress with hundreds of concrete blockhouses, mortar installations, and machine gun nests. It was protected by 2 000 Japanese soldiers.
3. Admiral Miwa Japanese Navy sent four submarines with fourteen kaiten torpedoes between them to Iwo Jiwa between February 20-3.
a. Only few submarines were available after severe losses in the Marianas and Leyte.
4. By the end of US airfield raids, Iwo Jima was left with less than 10 of the initial 80 Zeke planes and only 9 Kate torpedo bombers.
Size of American forces
1. Overall command was under Admiral Raymond Spruance. Admiral R.K. Turner oversaw the support and amphibious elements of the incoming invasion.
2. There was an assault-force of 80 000 Marines from the V Amphibious Corps, with a follow-up force of 30 000 army troops was available in the combined invasion fleet.
3. The invasion armada totalled over 1000 warships, including 7 aircraft carriers.
Results and Significance of Iwo Jima
1. Despite greater numbers, preliminary attacks, and superiority in both sea and air, US casualties were 25 000. Iwo demonstrated the brutality of guerrilla warfare in the Pacific Theatre, which was again reemphasized in Okinawa. This stressed the need for a speedy end to the war.
2. Iwo Jima was harsh for US soldiers because the Japanese understood that death was inevitable and victory was impossible—therefore each man vowed to kill 10 Americans before he died. Of over 20 000 Japanese troops, only 216 were taken alive.
3. The US used three airfields mainly for long range fighters (P series) to escort B-29s in attacks against central Honshu. Iwo also became a base for reconnaissance and shipping strikes by naval shore-based patrol planes.
a. Raids on the Home Islands hurt Japanese morale.
b. 1100 escort fighters and over 3000 aerial sorties launched against Japan.
4. For the US it became a northern outpost for protecting the Marianas.
5. Iwo airfields served as an emergency landing point for B-29s, and for the next five months 2 400 B-29s made forced landings.
Strategic Importance of Iwo Jima
“The purpose of these occupations was to acquire additional airfield sites in order to increase the weight of our shore-based air attacks against the Home Islands, to complete the air-sea blockade of Japan, to facilitate preparations for an invasion of the Home Islands, and to maintain unremitting military pressure against Japan.” US Strategic Bombing Survery, Campaigns of the Pacific War. U.S. Government Printing Office, 1946.
Historiography
David Rees, The Defeat of Japan
Rees states that despite high casualties, Iwo Jima was vital for the US because it resulted in the turning point of the American aerial attacks by allowing a base for the Tokyo bombings to occur. “Iwo Jima was soon used as a base for long-range P-51 Mustang and P-47 Thunderbolt fighters to escort the bombers on a new cycle of daylight incendiary attacks against Japan.”
Rees states that despite high casualties, Iwo Jima was vital for the US because it resulted in the turning point of the American aerial attacks by allowing a base for the Tokyo bombings to occur. “Iwo Jima was soon used as a base for long-range P-51 Mustang and P-47 Thunderbolt fighters to escort the bombers on a new cycle of daylight incendiary attacks against Japan.”
RS Thompson Empires on the Pacific
Thompson states that the Japanese “regarded Iwo Jima as part of the sacred homeland. As such, it was to be defended to the death.” Therefore he argues that US victory was most significant in reiterating the decline of Japan’s Empire and bringing dishonour to the Emperor.
Thompson states that the Japanese “regarded Iwo Jima as part of the sacred homeland. As such, it was to be defended to the death.” Therefore he argues that US victory was most significant in reiterating the decline of Japan’s Empire and bringing dishonour to the Emperor.
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