Editing Operation Downfall (section)

==Planning==
[[File:FDR conference 1944 HD-SN-99-02408.JPEG|thumb|Nimitz, MacArthur and Leahy holding a conference with [[Franklin D. Roosevelt|FDR]].]]
Responsibility for the planning of Operation Downfall fell to American commanders [[Fleet Admiral (United States)|Fleet Admiral]] [[Chester Nimitz]], [[General of the Army (United States)|General of the Army]] [[Douglas MacArthur]] and the [[Joint Chiefs of Staff]]—Fleet Admirals [[Ernest King]] and [[William D. Leahy]], and Generals of the Army [[George Marshall]] and [[Henry H. Arnold]] (the latter being the commander of the [[United States Army Air Forces|U.S. Army Air Forces]]).{{sfn|Skates|p=18}}

At the time, the development of the [[atomic bomb]] was a very closely guarded secret, known only to a few top officials outside the [[Manhattan Project]] (and to the Soviet espionage apparatus, which had managed to infiltrate or recruit agents within the program, despite the tight security around it), and the initial planning for the invasion of Japan did not take its existence into consideration. Once the atomic bomb became available, General Marshall envisioned using it to support the invasion if sufficient numbers could be produced in time.{{r |Perret 1991}}

The [[Pacific War]] was not under a single Allied [[commander-in-chief]] (C-in-C). Allied command was divided into regions: by 1945, for example, Chester Nimitz was the Allied C-in-C [[Pacific Ocean Areas]], while Douglas MacArthur was Supreme Allied Commander, [[South West Pacific Area]], and Admiral [[Louis Mountbatten, 1st Earl Mountbatten of Burma|Louis Mountbatten]] was the Supreme Allied Commander, [[South East Asia Command]]. A unified command was deemed necessary for an invasion of Japan. [[Interservice rivalry]] over who it should be (the [[United States Navy]] wanted Nimitz, but the [[United States Army]] wanted MacArthur) was so serious that it threatened to derail planning. Ultimately, the Navy partially conceded, and MacArthur was to be given total command of all forces if circumstances made it necessary.{{sfn|Skates|pp=55–57}}

===Considerations===
The primary considerations that the planners had to deal with were time and casualties—how they could force Japan's surrender as quickly as possible with as few Allied casualties as possible. Before the [[First Quebec Conference]], a joint Canadian{{endash}}British{{endash}}American planning team had produced a plan ("Appreciation and Plan for the Defeat of Japan") which did not call for an invasion of the Japanese Home Islands until 1947–48.{{sfn|Skates|p= 37}}{{sfn |Spector|pp= 276–77}} The American Joint Chiefs of Staff believed that prolonging the war to such an extent was dangerous for national morale. Instead, at the Quebec conference, the [[Combined Chiefs of Staff]] agreed that Japan should be forced to surrender not more than one year after [[Victory in Europe Day|Germany's surrender]].<ref>''Defeating Japan: The Joint Chiefs of Staff and Strategy in the Pacific War'', Charles F. Brower p. 59</ref><ref>''One Hundred Years of Sea Power: The U.S. Navy, 1890–1990'', George W. Baer p. 240</ref>

The United States Navy urged the use of a [[blockade]] and airpower to bring about Japan's capitulation. They proposed operations to capture airbases in nearby [[Shanghai]], [[Republic of China (1912–1949)|China]], and [[Korea]], which would give the United States Army Air Forces a series of forward airbases from which to bombard Japan into submission.{{sfn|Skates|pp=44–50}} The Army, on the other hand, argued that such a strategy could "prolong the war indefinitely" and expend lives needlessly, and therefore that an invasion was necessary. They supported mounting a large-scale thrust directly against the Japanese homeland, with none of the side operations that the Navy had suggested. Ultimately, the Army's viewpoint prevailed.{{sfn|Skates|pp=53–54}}

Physically, Japan made an imposing target, distant from other landmasses and with very few beaches geographically suitable for sea-borne invasion. Only [[Kyūshū]] (the southernmost island of Japan) and the beaches of the [[Kantō region|Kantō Plain]] (both southwest and southeast of [[Tokyo]]) were realistic invasion zones. The Allies decided to launch a two-stage invasion. Operation Olympic would attack southern Kyūshū. Airbases would be established, which would give cover for Operation Coronet, the attack on [[Tokyo Bay]].{{citation needed|date = July 2014}}

===Assumptions===
While the geography of Japan was known, the U.S. military planners had to estimate the defending forces that they would face. Based on intelligence available early in 1945, their assumptions included the following:{{sfn|Sutherland|p=2}}
* "That operations in this area will be opposed not only by the available organized military forces of the Empire, but also by a fanatically hostile population."
* "That approximately three (3) hostile [[Division (military)|divisions]] will be disposed in Southern Kyushu and an additional three (3) in Northern Kyushu at initiation of the Olympic operation."
* "That total hostile forces committed against Kyushu operations will not exceed eight (8) to ten (10) divisions and that this level will be speedily attained."
* "That approximately twenty-one (21) hostile divisions, including depot divisions, will be on Honshu at the initiation of [Coronet] and that fourteen (14) of these divisions may be employed in the Kanto Plain area."
* "That the enemy may withdraw his land-based air forces to the Asiatic Mainland for protection from our neutralizing attacks. That under such circumstances he can possibly amass from 2,000 to 2,500 planes in that area by exercising a rigid economy, and that this force can operate against Kyushu landings by [[Staging area|staging]] through homeland fields."

===Olympic===
[[File:Operation Olympic.jpg|thumb|Operation Olympic was planned to attack southern Japan.]]

Operation Olympic, the invasion of Kyūshū, was to begin on "X-Day", which was scheduled for November 1, 1945. The combined Allied naval armada would have been the largest ever assembled, including 42 [[aircraft carrier]]s, 24 [[battleship]]s, and 400 [[destroyer]]s and [[destroyer escort]]s. Fourteen U.S. divisions and a "division-equivalent" (two [[regimental combat team]]s){{Sfn |Giangreco|2009|p=40}} were scheduled to take part in the initial landings. Using [[Okinawa Island|Okinawa]] as a staging base, the objective would have been to seize the southern portion of Kyūshū. This area would then be used as a further staging point to attack Honshu in Operation Coronet.

Olympic was also to include a [[Military deception|deception]] plan, known as [[Operation Pastel]]. Pastel was designed to convince the Japanese that the Joint Chiefs had rejected the notion of a direct invasion and instead were going to attempt to encircle and bombard Japan. This would require capturing bases in [[Taiwan|Formosa]], along the Chinese coast, and in the [[Yellow Sea]] area.{{sfn|Skates|p=160}}

Tactical air support was to be the responsibility of the [[Fifth Air Force|Fifth]], [[Seventh Air Force|Seventh]], and [[Thirteenth Air Force]]s. These were responsible for attacking Japanese airfields and transportation arteries on Kyushu and Southern Honshu (e.g. the [[Kanmon Railway Tunnel|Kanmon Tunnel]]) and for gaining and maintaining air superiority over the beaches. The task of strategic bombing fell on the [[United States Strategic Air Forces in the Pacific]] (USASTAF)—a formation which comprised the [[Eighth Air Force|Eighth]] and [[Twentieth Air Force|Twentieth]] air forces, as well as the British [[Tiger Force (air)|Tiger Force]]. USASTAF and Tiger Force were to remain active through Operation Coronet. The [[Twentieth Air Force]] was to have continued its role as the main Allied [[strategic bombing|strategic bomber]] force used against the Japanese home islands, operating from airfields in the [[Mariana Islands]]. Following the end of the war in Europe in May 1945, plans were also made to transfer some of the heavy bomber groups of the veteran Eighth Air Force to airbases on Okinawa to conduct strategic bombing raids in coordination with the Twentieth.<ref name= "usafhra1">{{Cite web|title=Document Detail for IRISNUM= 00219137|url= http://airforcehistoryindex.org/data/000/219/137.xml|website= Air force history index}}</ref> The Eighth was to upgrade their [[B-17 Flying Fortress]]es and [[B-24 Liberator]]s to [[B-29 Superfortress]]es (the group received its first B-29 on August 8, 1945).<ref name="usafhra1"/> In total, General Henry Arnold estimated that the bomb tonnage dropped in the Pacific Theater by USAAF aircraft alone would exceed 1,050,000 tons in 1945 and 3,150,000 tons in 1946, excluding the blast yields of nuclear weapons.<ref>[https://oneworld.fas.org/fulltext.pdf One World Or None: A Report to the Public on the Full Meaning of the Atomic Bomb]. Article "Air Force in the Atomic Age" by General H. Arnold. Retrieved January 29, 2024</ref>

Before the main invasion, the offshore islands of [[Tanegashima]], [[Yakushima]], and the [[Koshikijima Islands]] were to be taken, starting on X−5.{{sfn|Skates|p=184}} The invasion of Okinawa had demonstrated the value of establishing secure anchorages close at hand, for ships not needed off the landing beaches and for ships damaged by air attack.

Kyūshū was to be invaded by the [[Sixth United States Army]] at three points: [[Miyazaki, Miyazaki|Miyazaki]], [[Ariake, Kagoshima|Ariake]], and [[Kushikino, Kagoshima|Kushikino]]. If a clock were drawn on a map of Kyūshū, these points would roughly correspond to 4, 5, and 7 o'clock, respectively. The 35 landing beaches were all named for automobiles: [[Austin Motor Company|Austin]], [[Buick]], [[Cadillac (automobile)|Cadillac]], and so on through to [[Stutz Bearcat|Stutz]], [[Winton automobile|Winton]], and [[Lincoln-Zephyr|Zephyr]].{{refn|Beach Organization for Operation against Kyushu; from COMPHIBSPAC OP Plan A11-45, August 10, 1945. {{harvnb|Skates|loc= pictorial insert}}.}} With one [[corps]] assigned to each landing, the invasion planners assumed that the Americans would outnumber the Japanese by roughly three to one. In early 1945, Miyazaki was virtually undefended, while Ariake, with its good nearby harbor, was heavily defended.

The invasion was not intended to conquer the entire island, just the southernmost third of it, as indicated by the dashed line on the map labeled "general limit of northern advance". Southern Kyūshū would offer a staging ground and a valuable airbase for Operation Coronet.

After the name Operation Olympic was compromised by being sent out in unsecured code, the name Operation Majestic was adopted.

===Coronet===
[[File:Operation Coronet Kantō.jpg|thumb|Operation Coronet was planned to take Tokyo.]]

Operation Coronet, the invasion of [[Honshu]] at the [[Kantō Plain]] south of the capital, was to begin on "Y-Day", which was tentatively scheduled for March 1, 1946.{{Sfn |Giangreco|2009|p=169}}  Coronet would have been even larger than Olympic, with up to 45 U.S. divisions assigned for both the initial landing and follow-up<ref>{{cite book |author1=War Department |title=History of Planning Division: Volume 6 (ASF-P-SL-1) |date=March 24, 1945 |page=27 |url=https://cgsc.contentdm.oclc.org/digital/collection/p4013coll8/id/1910 |access-date=May 21, 2023 |chapter=Part 1}}</ref> (by comparison, [[Operation Overlord|the invasion of Normandy]] deployed twelve divisions in the initial landings<!--10 full divisions and 4 brigades, using 2 brigades/division-->). In the initial stage, the [[First United States Army|First Army]] would have invaded at [[Kujūkuri Beach]], on the [[Bōsō Peninsula]], while the [[Eighth United States Army|Eighth Army]] invaded at [[Hiratsuka]], on [[Sagami Bay]]; these armies would have comprised 25 divisions between them.{{Sfn |Giangreco|2009|p=168}}  Later, a follow-up force of up to twenty additional U.S. divisions and up to five or more British Commonwealth divisions would have landed as reinforcements.{{sfn|Giangreco|2009|pp=26, 62}}<ref>History of Planning Division, ASF vol. 6 part 1 p. 29</ref> The Allied forces would then have driven north and inland, encircling Tokyo and pressing on toward Nagano.

===Redeployment===
{{See also|Operation Downfall order of battle}}
Olympic was to be mounted with resources already present in the Pacific, including the [[British Pacific Fleet]], a [[Commonwealth of Nations|Commonwealth]] formation that included at least eighteen aircraft carriers (providing 25% of the Allied air power) and four battleships.

Tiger Force, a joint Commonwealth long-range [[heavy bomber]] unit, was to be transferred from [[Royal Air Force|RAF]], [[Royal Australian Air Force|RAAF]], [[Royal Canadian Air Force|RCAF]] and [[Royal New Zealand Air Force|RNZAF]] units and personnel serving with [[RAF Bomber Command]] in Europe. In 1944, early planning proposed a force of 500–1,000 aircraft, including units dedicated to [[aerial refueling]]. Planning was later scaled back to 22 squadrons and, by the time the war ended, to 10 squadrons: between 120 and 150 [[Avro Lancaster]]s/[[Avro Lincoln|Lincolns]], operating out of airbases on Okinawa. Tiger Force was to have included the elite [[No. 617 Squadron RAF|617 Squadron]], also known as "The Dambusters", which carried out specialist bombing operations.

Initially, US planners also did not plan to use any non-US Allied ground forces in Operation Downfall. Had reinforcements been needed at an early stage of Olympic, they would have been diverted from US forces being assembled for Coronet—for which there was to be a massive redeployment of units from the US Army's [[South West Pacific Area (command)|Southwest Pacific]], [[China Burma India Theater|China-Burma-India]] and [[European Theater of Operations, United States Army|European]] commands, among others. These would have included spearheads of the war in Europe such as the [[US First Army]] (15 divisions) and the Eighth Air Force. These redeployments would have been complicated by the simultaneous demobilization and replacement of highly experienced, time-served personnel, which would have drastically reduced the combat effectiveness of many units.{{citation needed|date=October 2009}}

U.S. commanders rejected the Australian government’s early request for inclusion of an [[Australian Army]] infantry division in the first wave (Olympic).{{sfn|Day|p = 297}} Not even the initial plans for Coronet envisaged landing units from Commonwealth or other Allied armies on the Kantō Plain in 1946.{{sfn|Skates|p= 229}} The first official "plans indicated that assault, followup, and reserve units would all come from US forces".{{sfn|Skates|p= 229}}
By mid-1945—when plans for Coronet were being reworked—many other Allied countries had "offered ground forces, and a debate developed" amongst Western Allied political and military leaders, "over the size, mission, equipment, and support of these contingents".{{sfn|Skates|p= 229}} Following negotiations, it was decided that Coronet would include a joint [[Commonwealth Corps]], made up of infantry divisions from the Australian, [[New Zealand Army|New Zealand]], [[British Army|British]] and [[Canadian Army|Canadian]] armies. Reinforcements would have been available from those countries, as well as other parts of the Commonwealth. However, MacArthur blocked proposals to include an [[British Indian Army|Indian Army]] division because of differences in language, organization, composition, equipment, training and doctrine.{{sfn |Day| p=299}}{{Sfn | Skates| p=230}} He also recommended that the corps be organized along the lines of a U.S. corps, should use only U.S. equipment and logistics, and should train in the U.S. for six months before deployment; these suggestions were accepted.{{sfn|Day|p=299}} 

The British Government suggested that: Lieutenant-General Sir [[Charles Keightley]] should command the Commonwealth Corps, a combined Commonwealth fleet should be led by Vice-Admiral Sir [[William Tennant (Royal Navy officer)|William Tennant]], and that—as Commonwealth air units would be dominated by the RAAF – the Air Officer Commanding should be Australian.<ref>Gavin Long, 1963, Official Histories. ''Australia in the War of 1939–1945''. Series 1 – Army, Volume VII – The Final Campaigns, 1st ed., Canberra, Australian War Memorial p. 549.</ref> However, the Australian government questioned the appointment of Keightley, an officer with no experience in fighting the Japanese. [[Frederick Shedden]] suggested that Lieutenant General [[Leslie Morshead]], an Australian who had been carrying out the [[New Guinea campaign|New Guinea]] and [[Borneo campaign (1945)|Borneo campaigns]], should be appointed. The war ended before the details of the corps were finalized.{{sfn|Horner|p=418}}

===Projected initial commitment===
{|class="wikitable" style="text-align: right;"
!Operation
!Olympic<ref>[http://apps.dtic.mil/dtic/tr/fulltext/u2/a637722.pdf U.S. Army, Sixth Army Field Order 74, 28 July 1945] {{Webarchive|url=https://web.archive.org/web/20220716112107/http://apps.dtic.mil/dtic/tr/fulltext/u2/a637722.pdf |date=July 16, 2022 }} Retrieved November 6, 2021</ref>
!Coronet<ref>[https://apps.dtic.mil/sti/pdfs/ADA637723.pdf Staff Study Operations "Coronet" 15 August 1945] Retrieved November 6, 2021</ref>
|-
!Personnel
|705,556
|1,171,646
|-
!Vehicles
|136,812
|222,514
|-
!Shipping troop lift requirement<br>(dwt)
|1,205,730<ref name="Combined Arms Research Laboratory pp. 26">{{citation |url=http://cgsc.cdmhost.com/cdm/ref/collection/p4013coll8/id/3387 |date=May 25, 1945 |title=Downfall: Stategic Plan 1st Edition |publisher=General Headquarters, United States Army Forces in the Pacific |via= Combined Arms Research Laboratory |archive-url=https://web.archive.org/web/20140223031119/http://cgsc.cdmhost.com/cdm/ref/collection/p4013coll8/id/3387 |archive-date=February 23, 2014 }} p. 26, Retrieved March 3, 2016</ref>
|1,741,023
|-
!Infantry divisions
|11
|20
|-
!Marine divisions
|3
|3
|-
!Armored divisions
|0
|2
|-
!Air groups
|40
|50<ref name="Combined Arms Research Laboratory pp. 26" />
|}

Figures for Coronet exclude values for both the immediate strategic reserve of 3 divisions as well as the 17 division strategic reserve in the U.S. and any British/Commonwealth forces.