Samuel J. Cox, Director, Naval History and Heritage Command
“The sooner the Americans come, the better… One hundred million die proudly” – Japanese propaganda slogan, summer 1945.
Fortunately, at Christmas 1945, Operation Magic Carpet was in full swing, with December the peak month as over 700,000 U.S. servicemen were returned in that month to the United States from the Pacific aboard several hundred U.S. Navy ships. Were it not for the end of the war in August 1945, the alternative would have been the bloodiest battle in U.S. and U.S. naval history had the first phase of Operation Downfall (the invasion of Japan) been executed as planned on X-day (1 November 1945) in Operation Olympic (the invasion of the southernmost Japanese home island of Kyushu). The U.S. invasion force, with British participation, for Olympic would have significantly exceeded that of Operation Overlord, the invasion of Normandy in June 1944. An even bigger operation, Coronet, was planned for March 1946, an invasion of the Kanto plain area near Tokyo. Fortunately, 100 Million Japanese didn’t have to die a “glorious death,” nor tens of thousands of Americans, nor 5,000 U.S. Sailors (Fleet Admiral Nimitz’s estimate) since neither Olympic or Coronet, nor the Japanese defensive plan, Ketsugo, were executed.
Japan’s situation in 1945 was desperate. Although Japan still had 4 million men under arms, well over half were essentially trapped in China and Manchuria (thanks to the U.S. Navy, especially submarines) and unavailable for the defense of the Japanese Home Islands. Nevertheless, in over two thousand years, Japan had never been successfully invaded. The most serious previous threat came from two Mongol invasion attempts in 1274 and 1281, both of which were thwarted by typhoons that caused massive ship and manpower losses. Although the story of the “Divine Wind (Kamikaze)” is what is most remembered, in each case the Japanese put up ferocious resistance ashore. In the 1274 invasion attempt, the Mongols were actually withdrawing when the storm hit, destroying some 200 out of 500−900 ships and killing as many as 13,000 of 30,000 men.
The 1281 invasion attempt went even worse for Kublai Khan’s Mongol invasion force (reputed to be over 4,400 ships and 142,000 men─probably greatly exaggerated but still a massive force for the time). By 1281, the Japanese had made extensive defensive preparations and the Mongol fleet sailed around for months trying to find a place to get ashore before the great typhoon finally wiped out most of the fleet. The Japanese executed any Mongols (and Koreans and Northern Chinese) who made it ashore, sparing only Southern Chinese, who the Japanese believed had been coerced by the Mongols; the Japanese made them slaves. Some accounts claim Mongol losses at over 100,000 men.
Ironically, had Operation Olympic gone forward with X-day on 1 November 1945, it too would have been severely impacted by a typhoon. The Pacific typhoon season in 1945 was very active with 26 named storms, lasting from April into November. The first typhoon to hit after the Japanese surrender was Typhoon Ursula (7-15 September 1945) during which six transport aircraft flying from Okinawa to Manila were lost; all 120 recently liberated U.S. prisoners of war and aircrew aboard the aircraft died, the worst peacetime aerial disaster to that date.
However, in early October, Typhoon Louise took a sudden unexpected turn and on 9 October 1945 hit Okinawa full force, with hundreds of U.S. ships and vessels in Buckner Bay that didn’t have time to escape to sea. Twelve ships and craft were sunk, 222 were grounded, and another 32 severely damaged beyond repair. Casualties included 36 killed, 47 missing, and over 100 with serious injuries. Three destroyer-minesweepers and a destroyer escort were driven aground. The destroyer escort, Oberender (DE-444), was refloated, but the three destroyer-minesweepers were deemed not worth repair. About 107 amphibious craft were grounded, many of them wrecked beyond salvage, including four of six LSTs that were driven aground. Eighty percent of the buildings on Okinawa were destroyed or severely damaged, many still packed with war supplies. All 60 aircraft on Okinawa airfields were damaged. Only a month earlier, hundreds of aircraft were crammed on Okinawa airfields as well as many more ships and amphibious craft. The toll would have been far higher had Operation Olympic been underway. Instead, the vast majority of ships and aircraft were gone. Estimates shortly after the typhoon concluded that Operation Olympic would have been delayed by 45 days, which then would have put it in the teeth of winter storm season (in planning for Olympic, 1 December had been assessed as the last feasible date for the operation).
Operation Ketsugo (“Decisive Operation”)
Although the U.S. invasion force for Operation Olympic was massive, so to were Japanese preparations to counter it. Japanese Intelligence correctly estimated that the main objective for the initial U.S. landings would be southern Kyushu, specifically the Kagoshima Bay area, in order to establish an anchorage for Navy units and airfields to provide better air cover and close air support for the operation and follow-on operations. Southern Kyushu was just within the maximum range of U.S. fighters flying from Okinawa, one reason the Japanese assessed southern Kyushu would be the initial objective. The Japanese also correctly assessed that the U.S. would not attempt to take the entire island, but at some point would assume a defensive posture (to defend the new airfields) in preparation for the next planned major landings, which the Japanese also correctly believed to be near Tokyo.
The Japanese also with uncanny precision predicted the exact beaches on Kyushu that would be the target of the first landings. Although the Japanese initially thought the landings might occur as early as July, they changed their estimate based on the length of time it took the U.S. to capture Okinawa and of the usual end of typhoon season (October). The Japanese accurately predicted that the landings would occur at the very end of October or the beginning of November. As a result, the Japanese had ample time to reinforce Kyushu, which they did, going from one army division in the spring of 1945 to over 15 divisions by late summer. (Of note, some of the low-end U.S. casualty estimates, cherry-picked by those who argue the atomic bomb was not necessary, were derived before the full scope of Japanese defensive preparations on Kyushu became apparent).
The strategy for Operation Ketsugo was delineated in an Imperial Japanese Army directive of 8 April 1945. The Japanese determined that the strategic center of gravity for the operation was the will of the American people to continue to support the Allied goal of “unconditional surrender” in the face of massive casualties. The Japanese assessed that the critical U.S. weakness was the ability to sustain such extremely high casualties. Thus, the primary objective of Ketsugo was not to hold territory or destroy equipment, but to kill as many Americans as possible regardless of the cost to the Japanese. The objective was to break the will of the American people to sustain such high casualties so that the war could be ended with a negotiated settlement that did not lead to foreign occupation of Japan. It is also apparent from Japanese plans that they intended to throw everything they had (at least in terms of aircraft and naval vessels) into the defense of Kyushu with the intent to kill as many Americans as possible at the beachhead. Thus, American troop transports and amphibious ships were identified as the primary targets. Although the Japanese did not have the means to get their entire army onto Kyushu for logistical (and air threat) reasons, the Japanese did not intend to hold back aircraft or naval vessels for the expected follow-on landings near Tokyo.
The specific plan for the defense of Kyushu was Ketsugo No. 6 (there were other Ketsugo plans for potential landings in other locations, but No. 6 was given the highest priority). The defense of Kyushu was the responsibility of the 16th Area Army, made up of three armies with a total of 15 divisions, seven independent mixed brigades and independent tank brigades, and two coastal defense divisions. By the time of the Japanese surrender, this force had reached a strength of over 900,000 men. This exceeded the 582,500 men in 13 U.S. assault divisions planned for the landings on Kyushu. The total U.S. force on Kyushu was planned to top out a 766,700.
The effects of U.S. naval gunfire figured prominently in Japanese defensive planning. The Japanese battle plans envisioned fighting in such close contact with U.S. forces that the battle lines would be so confused that U.S. advantages in close air support and naval gunfire support would at least be partially mitigated.
During the course of the war, the Japanese had learned much the hard way. The defensive preparations on Kyushu were based on the “Three Basic Principles on How to Fight Americans” derived from previous combat experience. In a nutshell, these principles were:
- Positions should be constructed beyond the effective range of enemy naval bombardment.
- Cave-type positions should be constructed for protection against air raids and naval bombardment.
- Inaccessible high ground should be selected as protection against flame-throwing tanks.
The Japanese first line of defense against the invasion of Kyushu was what was left of the Imperial Japanese Navy, as aircraft were not expected to be committed until troop transports were in close proximity to the beachhead. Of the 46 remaining Japanese submarines, about 38 were operational in Japanese waters and would be the first thing U.S. forces would encounter. Although an opportunity to sink a carrier would not be passed up, the troop transports were top priority. A few of the Japanese submarines were equipped to carry Kaiten manned-suicide torpedoes and about 120 Kaitens would be immediately available for use, although some estimates for the number of Kaitens that would have been available by November range as high as 1,000. Although the Kaitens had proved largely ineffective in open-ocean use, the Japanese anticipated much better success in confined and crowded waters of an amphibious beachhead, which probably would have been the case.
The Japanese already had quite a few midget submarines, which had been held back thus far, and were building more. The Japanese expected to have about 540 five-man “Koryu” midget submarines (two torpedoes or explosive charge) and about 740 of the more advanced “Kairyu” midget submarines (also two torpedoes or explosive charge) ready for use by November. However, Koryu production was severely impacted by bombing and only 110 were complete when the war ended, and only 250 of the Kairyu had been completed.
Once the American assault was underway, the Japanese navy would shift to phase two, expecting to commit all 19 of their surviving operational destroyers to one-way suicide attacks on the amphibious ships. The Japanese also intended to commit about 3,300 Shinyo suicide boats (most army-manned and some navy-manned). Shinyo’s came in various versions; the navy boats generally had a 550-pound explosive charge in the bow, while the army ones had two depth charges that could be rolled off the stern as the boat made a getaway (the army boats were not originally intended as suicide craft). The estimated numbers of Shinyo are very squishy, with some as high as 6,300. What is pretty firm is that by the end of the war 800 Shinyo had been assigned to the 16th Area Army on Kyushu.
The Japanese navy also intended to employ suicide frogmen, “Fukuryu,” operating from prepared underwater shelters in the beachhead area (some of these shelters were designed to hold as many as 18 frogmen). Equipped with diving suits and oxygen, the Fukuryu would swim to the surface with explosive charges to take out landing craft as they went overhead. The navy expected to have about 4,000 Fukuryu equipped and trained by November 1945 for the “Water’s Edge Surprise Attack Force.”
Air operations in support to Ketsugo No. 6 were the responsibility of the 5th Naval Air Fleet and 6th Air Army, both under centralized control of the Air General Army. (Unlike how the Japanese fought the rest of the war, Ketsugo stressed joint operations and unified command and control instead of the army and navy each doing its own thing.) There were numerous airfields available for use on nearby Shikoku and Honshu Islands. However, the 60 or so airfields on Kyushu, which were under almost daily U.S. air attacks, would be used only for staging kamikaze attacks.
During the kamikaze attacks during the battle of Okinawa the majority of Japanese kamikazes fell to U.S. Navy fighters during the long transit to Okinawa, well before they reached U.S. ships off Okinawa. The Kyushu situation would be different. The Japanese intended to hold back air attacks until U.S. ships (especially troop transports) were in close proximity to the beach. The Japanese would make maximum use of short flight times and terrain masking to achieve surprise and negate the U.S. radar advantage. Although Fleet Admiral Nimitz had a plan to conduct a feint on Kyushu in October with intent to draw out Japanese aircraft to be downed by battleships and cruisers festooned with antiaircraft weapons, the Japanese had no intention of taking the bait. Aircraft were to remain dispersed, camouflaged, and hidden until the amphibious ships were close to shore. (The lack of Japanese air activity in the last months of the war resulted in an erroneous U.S. assessment that the Japanese were out of aviation fuel. In fact, the Japanese had hoarded enough to execute the Ketsego plan.)
The Japanese army air attack plan called for aircraft to attack in waves of 300-400 aircraft, at a rate of one wave per hour, day and night, until all aircraft and pilots were gone. The navy preferred to conduct attacks at twilight, and the discussion was still inconclusive at the end of the war. Nevertheless, this level of effort would have resulted in more kamikaze attacks in three hours than in the three months of the Okinawa campaign, and would have had a good prospect of saturating the defenses of transports when they were most vulnerable.
Estimates of how many aircraft the Japanese had at the end of the war vary considerably, although the common theme was that the U.S. underestimated the number. Throughout the summer of 1945, the Intelligence estimates kept growing at an alarming rate. Many Japanese aircraft destroyed on the ground by U.S. air strikes were actually wooden dummies. The Japanese probably had about 12,700 aircraft of all types (5,600 army and 7,000 navy – yes they don’t add up). Many of these were not combat aircraft. However, the Japanese had shown during the Battle of Okinawa that even wooden bi-plane trainers could sink destroyers, and such aircraft would be even more uniquely well suited for attacks close-in to shore against troop transports. Such wood and canvas aircraft also had the advantage of low radar-cross section and greatly impeded the effectiveness of U.S. radar-proximity fuzes. At the end of the war, Japan only had about 8,000 decently-trained pilots (this number is squishy too). The Japanese had crash programs to train more pilots and some estimates indicate they may have had 18,600 trained well enough by November to conduct a one-way suicide attack. The Japanese intention was to throw every aircraft that could fly into kamikaze attacks against U.S. ships while they were most vulnerable trying to get troops ashore, and were modifying almost all their aircraft to do so.
At Kyushu, the Japanese ground forces intended to use a layered defensive strategy that combined defenses at the beach with extensively dug-in positions inland and foot mobile reserves for eventual night counterattack. Earlier in the war, such as at Tarawa, the Japanese learned that trying to defend at the beach was not a good idea in the face of U.S. naval gunfire. However, they had also learned how to build better-concealed and constructed beach defenses that could withstand all but a direct hit by a heavy caliber shell. The Japanese had even sent a team to Germany in late 1944 to learn from the German experience at Normandy. Behind the beach defenses was the “foreground zone,” much like the Japanese defenses on Iwo Jima and Okinawa, with mortars and artillery sited on the reverse slope of the first ridge (and camouflaged from air attack), close enough to engage the beachhead before U.S. troops could dig in. Further inland was the “main zone of resistance,” outside the range or inaccessible to naval gunfire, deeply dug-in against air attack, with caves and extensive tunnel systems enabling infiltration behind the lines of advancing U.S. forces.
Lastly, the Japanese intended to mobilize the “Civilian Volunteer Corps,” which weren’t actually volunteers. Under the repeated bombardment of variations of the slogan, “The glorious death of the 100 million,” all males ages 15-60 and all females ages 17-40 were to be mobilized. Many had already been trained in the use of hand grenades, swords, knives, bamboo spears, or anything with a sharp point, with special emphasis on night infiltration behind U.S. lines. The Japanese deliberately had no plan to evacuate civilians from the battle area or to declare “open cities.” The civilians were expected to fight and die to the last with the soldiers, and as a result of extensive Japanese propaganda most Japanese civilians by late 1945 were resigned to that fate. The civilian population of Kyushu was 2,400,000. Whether they died fighting, were caught in the crossfire, committed suicide (as had many on Saipan and Okinawa), or were executed for not fighting, many tens of thousands of them were going to die. The Japanese also planned, that in the event of an invasion of Japan, all Allied prisoners of war were to be executed; that would have been about 15,000 dead Americans (and 100,00 total Allied), not counting any in the invasion force.
The intent of Operation Downfall was to invade, occupy, and bring about the unconditional surrender of Japan within 18 months of the defeat of Germany. It would require 1,700,000 U.S. troops, according to the plan. American political and military leaders believed that it was essential to bring about the end of the war as quickly as possible, as war fatigue in the American population was becoming increasingly apparent. The Japanese assessment that high casualties were America’s strategic vulnerability was to a large degree correct. In the first years of the war (aside from Pearl Harbor), overall U.S. casualties were relatively light (especially compared to other major combatant nations). However, this changed in mid-1944 with the invasion of Normandy and the Marianas, the Battle of the Bulge, the campaign in the Philippines, Iwo Jima, and Okinawa. By late 1944, U.S. Army casualties had skyrocketed to 65,000 per month. There was increasing concern whether the U.S. could induct enough new manpower to keep up with losses at that rate. Hence, the U.S. Army leadership in particular was in no mood to drag out the war against Japan with the Navy’s preferred approach of slow strangulation with sea blockade and aerial bombardment.
Although General of the Army Douglas MacArthur, Commander-in-Chief of the Southwest Pacific Area of Operations, was an outspoken critic of high-casualty, Navy-led operations like Tarawa, Saipan, Peleliu, and Iwo Jima, he was the most vociferous proponent of an invasion of Japan, despite the expected cost. Chief of Staff of the Army George Marshall was less enthusiastic, but firmly believed that an invasion was necessary. Marshall did become increasingly concerned as the intelligence estimates of the number of Japanese troops on Kyushu continued to climb along with casualty estimates. The bloody battles for Iwo Jima and Okinawa were a real shock. Casualties on Saipan had been bad enough, and initial planning for Downfall was based on the “Saipan ratio” of about one U.S. casualty for every seven Japanese defenders. By Okinawa, it was closer to one U.S. casualty for every one or two Japanese defenders. (Do the math on 900,000 Japanese troops fighting on their home soil on Kyushu, which explains while many U.S. leaders started getting cold feet on an invasion.)
On the Navy side, Chief of Naval Operations Fleet Admiral Ernest J. King was consistently opposed to an invasion (although he acquiesced to the necessity for detailed planning for Olympic) and on that score was in rare alignment with the U.S. Army Air Force. King supported establishing a lodgment on the coast of China (Operation Longtom) for a base to strangle Japan via blockade, although King’s vision of using the Chinese Army to do the dirty work of invading Japan was never realistic for many reasons. The Air Force believed they could bomb the Japanese into submission, although they were fast running out of cities to incinerate. Fleet Admiral William D. Leahy, roughly analogous to the Chairman of the Joint Chiefs of Staff, firmly believed that an invasion of Japan was neither necessary nor desirable. Fleet Admiral Chester Nimitz, Commander-in-Chief of the Pacific Ocean Area, was initially supportive of an invasion, but the carnage of Iwo Jima, Okinawa, and the kamikaze attacks changed his mind. Admiral Raymond Spruance, who would command the initial invasion of Kyushu and had first-hand experience at Saipan, Iwo Jima, and Okinawa, was not in favor of an invasion. Spruance recommended continued blockade and aerial bombardment to Nimitz, with the belief that the Japanese should be allowed to “stew in their own juices” for a while and “wither on the vine” as had been done with other Japanese strongholds in the war.
The timetable for Operation Downfall had been set by late March 1945 by the Joint Chiefs of Staff as 1 December 1945 for Operation Olympic (Kyushu) and 1 March 1946 for Operation Coronet (Kanto Plain/Tokyo). Nimitz recommended that the date for Olympic be moved forward to 1 November to avoid disruptive winter storms (also not expecting that the typhoon season would last longer than usual). Nimitz’ recommendation was accepted.
The planning for Downfall was complicated by major disagreements amongst the services as to whether MacArthur or Nimitz should be in charge. Ultimately, MacArthur was given “primary responsibility” and Nimitz “broad leeway to operate,” i.e., the problem of command and control was not completely resolved by the time the war ended. Eventually a compromise was reached such that all U.S. Army forces in the Pacific would fall under MacArthur’s command (even those in Nimitz’s area of responsibility) and all U.S. Navy forces in the Pacific would fall under Nimitz (even those in MacArthur’s area, such as the SEVENTH Fleet). This was actually a significant step backwards for “jointness” and unity of command, but MacArthur’s chief of staff summed it up as, “Never again will U.S. Army troops serve under an admiral.” (Goldwater-Nichols got the last laugh on that though.)
A key meeting occurred in the White House Oval Office on 18 June 1945 with President Harry S. Truman, and Secretary of War Henry Stimson, Secretary of the Navy James Forrestal, and the four Joint Chiefs (Leahy, Marshall, King, and Army Air Force General Hap Arnold). Marshall briefed that Kyushu was expected to be defended by 350,000 Japanese troops, as well as MacArthur’s estimate that the Japanese only had 2,500-3,000 aircraft (both estimates were way too low). All the service chiefs presented their views on the advisability of invading Japan, the likely cost in lives, and provided their recommendations. Leahy, King, and Arnold opposed an invasion, but concurred that planning needed to go forward. However, Truman sided with Marshall that an invasion was necessary, at least the first phase to take Kyushu. Truman then signed orders to shift the necessary additional troops from the European theater to the Pacific. Although Truman made a decision to go forward, it is likely that King believed there would be future reassessment and opportunity to forestall an invasion (technically, major decisions on operations required JCS unanimity, of which there wasn’t).
Meanwhile, over the summer of 1945, Intelligence estimates derived from Ultra code-breaking regarding the number of Japanese defenders on Kyushu continued to climb and by mid July had reached 680,000. As a result, casualty estimates for Operations Olympic and Downfall continued to climb, much based on the experience on Okinawa, and Intelligence that the Japanese were mobilizing more men in Japan and somehow managing to bring in more men back from China and Manchuria despite the blockade.
The U.S. Sixth Army, which would invade and occupy Kyushu, estimated 124,935 U.S. battle casualties, including 25,000 dead, plus 269,000 non-battle casualties (disease, accident, etc.) for Kyushu alone. The JCS came up with an estimate that a 90-day campaign on Kyushu would cost 156-175,000 battle casualties, with 38,000 killed in action. By late July, the JCS was forecasting 500,000 casualties at the high end and 100,000 at the low end. In late July 1945, the War Department provided an estimate that the entire Downfall operations would cause between 1.7 to 4 million U.S. casualties, including 400-800,000 U.S. dead, and 5 to 10 million Japanese dead. (Given that the initial Downfall plan called for 1,792,700 troops to go ashore in Japan, this estimate is indeed most sobering, and suggests many more troops than planned would need to be fed into a meat grinder). Other estimates in the U.S. government indicated U.S. deaths at 500,000 to 1 million. Which of these and other estimates would be the most accurate has been hotly debated over the years (and are caught up in the debate about whether the atomic bomb should have been used), and I’m not going to solve it. But it is clear that the cost of invading Japan would have been staggering for both the U.S. and the Japanese.
Planned U.S. Navy Organization for Operation Olympic
The U.S. Navy’s role in Operation Olympic called for virtually every Navy unit in the Pacific, in addition to many brought around from the European theater. For the first time in the war, the U.S. Navy had so many ships that the FIFTH Fleet and THIRD Fleet would be activated at the same time (and SEVENTH Fleet reduce to a handful of ships in Southeast Asia/Dutch East Indies). The FIFTH Fleet, commanded by Admiral Raymond Spruance, would conduct the amphibious assault on Kyushu and provide direct support with its own Fast Carrier Task Force (TF-58) and every pre-WWII battleship still afloat. The THIRD Fleet’s Fast Carrier Task Force (TF-38) and all the new fast battleships would provide strategic support by conducting strikes throughout Honshu and Hokkaido while also isolating Kyushu from reinforcement. A British Royal Navy Carrier Task Force (TF-37) was assigned to THIRD Fleet. For tactical airstrikes against Japan, the Navy and Air Force divided the airspace, with the Navy taking everything east of 135-degrees east and the Air Force everything west of it.
The THIRD Fleet, commanded by Admiral William F. Halsey, would commence strike operations on 18 October to isolate Kyushu, and hopefully draw out Japanese aircraft so they could be destroyed. On 24 October, the Fast Carrier Task Force would split into TF-38 and TF-58. After the split, THIRD Fleet would include 21 fast aircraft carriers with 1,826 aircraft, plus 11 fast battleships, 30 cruisers, and 107 destroyers. Under THIRD Fleet, TF-38 was designated the Second Fast Carrier Task Force, and would be commanded by Vice Admiral Jack Towers, who had relieved VADM John McCain. TF-38 would have eight Essex-class fleet carriers and four Independence-class light carriers with 1,266 aircraft. TF-38 would consist of three task groups; TG-38.1 commanded by RADM Arthur Davis, TG-38.2 commanded by RADM Thomas Sprague, and TG-38.3 commanded by RADM Clifton “Ziggy” Sprague.
The British Task Force (TF-37), would be commanded by Vice Admiral Bernard Rawlings, and included one task group of four fleet carriers (TG-37.6), commanded by VADM Phillip Vian and a second task group of one fleet carrier and four light carriers (TG-37.7) with a total of 560 British aircraft. Initially TF-37 would conduct diversionary attacks near Hong Kong before joining up with THIRD Fleet for attacks on the Japanese Home Islands.
FIFTH Fleet under ADM Raymond Spruance was huge, consisting 2,902 ships (not including landing craft) which would put 582,560 troops of the U.S. Sixth Army (including three Marine divisions) ashore at 35 beaches on Kyushu, building to a total of 766,700 troops ashore. FIFTH Fleet would include over 800 combatant ships and 1,500 transport ships, and would include 13 prewar battleships, 24 cruisers, 139 destroyers, and 167 destroyer escorts. FIFTH Fleet also included 20 amphibious command ships (AGC), 210 attack transports (APA), 12 troopships (AP), 84 attack cargo ships (AKA), 92 destroyer-transports (APD), 515 landing ship tank (LST), 16 landing ship dock (LSD), 360 landing ship medium (LSM), three hospital ships (AH), and numerous smaller patrol and mine warfare vessels and auxiliaries.
Organic air support for FIFTH Fleet would be provided by TF-58, designated the First Fast Carrier Task Force, commanded by VADM “Ted” Sherman. TF-58 would include six Essex-class fleet carriers, Enterprise (CV-6), and three light carriers. Additional organic air cover would be provided by the escort carrier task force (TF-55) commanded by RADM Calvin Durgin, with 16 escort carriers and 448 aircraft. Four of the escort carriers had Marine squadrons embarked and three were designated “night carriers.” All told, FIFTH Fleet would receive direct support from 4,023 carrier and land-based (in the Ryukyus) aircraft, while 768 aircraft in the Marianas and 225 on Iwo Jima would provide indirect support attacking targets in Honshu. With the night carriers, including Enterprise, the force would be protected at night by a combat air patrol of at least 18 F6F-5N Hellcat night fighters and six land-based Air Force P-61 Black Widows. For the first time in the war, Airborne Early Warning coverage would be provided by radar-equipped carrier-based TBM-3W Avengers and land-based PB-1W (Navy AEW variant of the B-17 Flying Fortress). The force would also include 13 afloat and five landing force fighter direction teams. In addition to the aircraft innovations, FIFTH Fleet would be equipped with over 1,000 KGW-1 Loon cruise missiles (navalized version of reverse-engineered German V-1 “buzz bombs”), which would be fired from modified LSTs and escort carriers, and work was underway to launch them from PB4Y-2 Privateers (Navy version of B-24 bomber).
The Amphibious Force was designated TF-40 and would be under the command of Admiral Richmond “Kelly” Turner embarked on his flagship Eldorado (AGC-11). Also embarked on Eldorado would be Army General Walter Krueger, who commanded the Sixth Army. The Sixth Army was organized into four corps, with three divisions each, plus two independent divisions. These included V Amphibious Corps, with the 2nd, 3rd and 5th Marine Divisions, plus nine U.S. Army infantry divisions, plus a cavalry division and an airborne division. Also embarked on Eldorado was the Air Support Control Group (TG-40.10, commanded by RADM Mel Pride.
Admiral Kelly would also command the Advance Force (TF-41) which would arrive off Kyushu on 24 October 1945, with gunfire support, minesweeping, underwater demolition, hydrographic survey, and service and salvage groups. When the rest of the amphibious force arrived just before X-Day, TF-41 would dissolve and combine with TF-40. VADM Jesse Oldendorf would be in command of the gunfire and covering forces (TF 54), with the older battleships, most of which would be divided among several attack groups. The mine force (TF-56) was commanded by RADM Alexander Sharp, and the minesweepers would also be divided amongst the attack groups.
The Amphibious Force was divided into several attack groups, each with its own battleship/cruiser and escort carrier support:
The Third Attack Force (TF-43) would be commanded by VADM Theodore Wilkinson embarked on MOUNT OLYMPUS (AGC-8) and whose transports would embark the U.S. Army XI Corps. Supporting TF-43 would be the Third Fire Support Group (TG-41.3), commanded by RADM Richard Connolly, with six older battleships, six cruisers, 13 destroyers and 34 support ships, with four TF-55 escort carriers attached.
The Fifth Attack Force (TF-45) would be commanded by VADM Harry Hill, whose transports would embark the U.S. Marine V Amphibious Corps. Supporting TF-45 would be the Fifth Fire Support Group (TG-41.5), commanded by RADM Jerauld Wright, with four older battleships, ten cruisers, 14 destroyers, and 74 support ships, with four TF-55 escort carriers attached.
The Seventh Attack Force (TF-47) would be commanded by VADM Daniel Barbey, embarked on ANCON (AGC-4) and whose transports would embark the U.S. Army I Corps. Supporting TF-47 would be the Seventh Fire Support Group (TG-41.7), commanded by RADM Ingolf Kiland, with three older battleships, eight cruisers, 11 destroyers and 35 support ships, plus four TF-55 escort carriers attached.
Two other smaller attack forces included Western Attack Force (TF-42), commanded by RADM Glen Davis, supported by the Western Fire Support Group (TG-42.2) with the mission to seize outlying Islands. The Southern Attack Force (TF-44) would be commanded by RADM Robert Brisco, supported by the Southern Fire Support Group (TG-44.2).
Other major FIFTH Fleet formations included the Reserve Force (TF-48), commanded by RADM Bertram Rogers, with the U.S. Army IX Corps embarked. The Reinforcement Force (TF-49) would be commanded by RADM Arthur Struble (who would be the Commander of SEVENTH Fleet during the Korean War and Joint Task Force SEVEN for the Inchon landings). The Screen Group (TG-40.1) would be commanded by Commodore Frederick Moosbrugger, whose forces included the radar pickets and the screens for each of the other major formations.
In addition to this massive force, additional reinforcements by new construction and repaired ships would arrive in November. These would include repaired Essex (CV-9), Franklin (CV-13), Bunker Hill (CV-17), and San Jacinto (CVL-30), along with British carrier HMS Illustrious and the new Canadian night carrier HMCS Ocean. By December 1945, 40 fast carriers, and 25 battleships would be operating in support of Olympic or bombarding the other Japanese Home Islands.
With U.S. naval forces as large as that arrayed for Operation Olympic, victory was never in doubt. What was in doubt was the price to be paid. Without factoring in submarines, midget submarines, suicide boats, suicide frogmen, mines, or the Japanese advantage of short-range and terrain masking, nor the Japanese strategy of going after comparatively weakly defended troop ships, assuming that the Japanese could obtain the same ratio of hits per kamikaze as during the Okinawa campaign, the U.S. Navy could expect a minimum of 95 ships sunk and 995 damaged, with between 5,000 and 12,000 Sailors killed during Operation Olympic alone. This would have easily made it the most costly battle in U.S. naval history.
(Sources include: The Naval Siege of Japan 1945: War Plan Orange Triumphant, by Brian Herder: Osprey Publishing, 2020. Downfall: The End of the Imperial Japanese Empire, by Richard B, Frank: Penguin Books, 1999. Hell to Pay: Operation Downfall and the Invasion of Japan, 1945-1947, by D.M. Giangreco: Naval Institute Press, 2009. Twilight of the Gods: War in the Western Pacific, 1944-1945, by Ian Toll: W.W. Norton, Co., 2020. The Fleet at Flood Tide: America at Total War in the Pacific 1944-1945, by James D. Hornfischer: Bantam Books, 2016. Typhoons and Hurricanes: Pacific Typhoon at Okinawa, October 1945, NHHC document at history.navy.mil Nov 2017