Editing Manhattan Project (section)

== Atomic bombings of Hiroshima and Nagasaki ==
{{Main|Atomic bombings of Hiroshima and Nagasaki}}

=== Preparations ===
[[File:CGP-JPAP-112.jpg|thumb|[[Silverplate]] B-29 ''[[Straight Flush (B-29)|Straight Flush]]''. The tail code of the [[444th Bombardment Group]] is painted on for security reasons.|alt=A shiny metal four-engined aircraft stands on a runway. The crew pose in front of it.]]
The only Allied aircraft capable of carrying the {{convert|17|ft|m|adj=on}} long Thin Man or the {{convert|59|in|cm|adj=on}} wide Fat Man was the British [[Avro Lancaster]], but using a British aircraft would have caused difficulties with maintenance. Groves hoped that the American [[Boeing B-29 Superfortress]] could be modified to carry a Thin Man by joining its two [[bomb bay]]s together.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=379–380}} This became unnecessary after Thin Man was abandoned, as a Little Boy was short enough to fit into a B-29 bomb bay,{{sfn|Rhodes|1986|p=541}} but modifications were still required. The [[Air Force Materiel Command|Army Air Forces Materiel Command]] at [[Wright Field]], Ohio, began [[Silverplate]], the codename for the modification of the B-29, in November 1943. Test drops were carried out at [[Muroc Army Air Field]] and the [[Naval Ordnance Test Station]] in California with Thin Man and Fat Man [[pumpkin bomb]]s to test their ballistic, fuzing and stability characteristics.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=380–381}}

The [[509th Composite Group]] was activated on 17 December 1944 at [[Wendover Army Air Field]], Utah, under the command of Colonel [[Paul W. Tibbets]]. Its [[393rd Bombardment Squadron]], equipped with Silverplate B-29s, practiced long-distance flights over water and dropped pumpkin bombs.{{sfn|Groves|1962|pp=259–262}} A special unit known as [[Project Alberta]] was formed at Los Alamos under Parsons's command to assist in preparing and delivering the bombs.{{sfn|Groves|1962|pp=259–262}} The 509th Composite Group deployed to [[North Field (Tinian)|North Field]] on [[Tinian]] in July 1945.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=386–388}} Most of the components for the Little Boy left San Francisco on the [[cruiser]] {{USS|Indianapolis|CA-35|6}} on 16 July and arrived on Tinian on 26 July. The remaining components, which included six highly enriched uranium rings, were delivered by three [[Douglas C-54 Skymaster]]s of the 509th Group's 320th Troop Carrier Squadron.{{sfn|Campbell|2005|pp=39–40}} Two Fat Man assemblies traveled to Tinian in specially modified 509th Composite Group B-29s, and the first [[plutonium core]] went in a special C-54.{{sfn|Groves|1962|p=341}}

At the end of December 1944, worried by the heavy losses occurring in the [[Battle of the Bulge]], Roosevelt instructed Groves and Stimson that if the atomic bombs were ready before the war with Germany ended, they should be ready to drop them on Germany, but Japan was regarded as more likely.{{sfn|Groves|1962|p=184}} In late April 1945, a targeting committee was established to determine which cities should be targets, and it recommended [[Kokura]], [[Hiroshima]], [[Niigata (city)|Niigata]], and [[Kyoto]]. Stimson intervened, announcing that he would be making the targeting decision, and that he would not authorize the bombing of Kyoto on the grounds of its historical and religious significance.{{sfn|Groves|1962|pp=268–276}} [[Nagasaki]] was ultimately substituted.{{sfn|Groves|1962|p=308}} In May 1945, the [[Interim Committee]] was created to advise on wartime and postwar use of nuclear energy. The Interim Committee in turn established a scientific panel consisting of Arthur Compton, Fermi, Lawrence, and Oppenheimer; the scientific panel offered its opinion not just on the likely physical effects of an atomic bomb, but on its probable military and political impact. In a meeting on 1 June, the Interim Committee resolved that "the bomb should be used against Japan as soon as possible; that it be used on a war plant surrounded by workers' homes; and that it be used without prior warning".<ref>{{harvnb|Jones|1985|pp=530–532}}.</ref><ref>{{cite web |url=http://www.trumanlibrary.org/whistlestop/study_collections/bomb/large/documents/index.php?documentdate=1945-06-01&documentid=40&studycollectionid=abomb&pagenumber=8 |title=Notes of Meeting of the Interim Committee, June 1, 1945 |publisher=The Harry S Truman Library and Museum |pages=8–9 |access-date=March 2, 2011 |archive-date=May 14, 2011 |archive-url=https://web.archive.org/web/20110514053030/http://www.trumanlibrary.org/whistlestop/study_collections/bomb/large/documents/index.php?documentdate=1945-06-01&documentid=40&studycollectionid=abomb&pagenumber=8 |url-status=dead }}</ref>

At the [[Potsdam Conference]] in Germany, President [[Harry S. Truman]] told Stalin that the US had "a new weapon of unusual destructive force", without giving any details. As he showed "no special interest," Truman erroneously assumed that Stalin did not understand. In reality, Soviet spies had kept Stalin informed of the work and the planned test.<ref>{{harvnb|Holloway|1994|pp=116–117}}.</ref><ref>{{cite web|url=https://history.state.gov/historicaldocuments/frus1945Berlinv02/d710a-97|title=Foreign Relations of the United States: Diplomatic Papers, The Conference of Berlin (The Potsdam Conference), 1945, Volume II|publisher=Office of the Historian|access-date=24 January 2024}}</ref><ref>{{cite book|last=Gordin|first=Michael|title=Red Cloud at Dawn: Truman, Stalin, and the End of the Atomic Monopoly|publisher=Farrar, Straus and Giroux|year=2009|pages=7–10}}</ref>

A strike order from General [[Thomas T. Handy]] to General [[Carl Spaatz]] was approved by Marshall and Stimson on 25 July which specified that the "first special bomb" be used "after about 3 August 1945," and that "additional bombs" would be used "as soon as made ready by the project staff".<ref>{{cite web|url=https://www.osti.gov/opennet/manhattan-project-history/Resources/order_drop.htm|title=Order to Drop the Atomic Bomb, Handy to Spaatz, July 25, 1945|publisher=Office of History and Heritage Resources, US Department of Energy|access-date=24 January 2024}}</ref> The operational plan was to drop the first bomb on 2 August, the second bomb on 10 August, and a third bomb around 24 August. However, due to weather conditions over Japan and the desire for visual bombing, the date of the first bombing mission was pushed back to 6 August, and the second was moved forward to 9 August.<ref>{{cite book|last=Gordin|first=Michael|title=Five Days in August: How World War II Became a Nuclear War|publisher=Princeton University Press|year=2007|pages=80, 90, 99}}</ref>

=== Bombings ===
On 6 August 1945, the ''[[Enola Gay]]'', a Boeing B-29 Superfortress of the 393d Bombardment Squadron, piloted by Tibbets, lifted off from North Field with a Little Boy in its bomb bay. Hiroshima, the headquarters of the [[2nd General Army]] and [[5th Division (Imperial Japanese Army)|Fifth Division]] and a port of embarkation, was the primary target, with Kokura and Nagasaki as alternatives. Parsons, the weaponeer in charge of the mission, completed the bomb assembly in the air to minimize the risks of a nuclear explosion in the event of a crash during takeoff.<ref>{{harvnb|Groves|1962|pp=315–319}}.</ref> The bomb detonated at an altitude of {{convert|1750|ft}} with a blast that was later estimated to be the equivalent of 13 kilotons of TNT.<ref>{{harvnb|Hoddeson|Henriksen|Meade|Westfall|1993|pp=392–393}}</ref> An area of approximately {{convert|4.7|sqmi|km2}} was destroyed. Japanese officials determined that 69% of Hiroshima's buildings were destroyed and another 6–7% damaged. Early estimates were that 66,000 people were killed and 69,000 injured; later re-estimations that included people ignored by previous methods, like Korean slave laborers and additional soldiers, concluded there might have been 140,000 dead from the attack by December 1945.<ref name="casualties">{{cite journal |last=Wellerstein |first=Alex |author-link=Alex Wellerstein |title=Counting the dead at Hiroshima and Nagasaki |journal=Bulletin of the Atomic Scientists |date=4 August 2020 |url=https://thebulletin.org/2020/08/counting-the-dead-at-hiroshima-and-nagasaki/ |access-date=23 January 2024}}</ref><ref name="USSBS">{{cite web |website=[[Harry S. Truman Presidential Library and Museum]] |title=U.S. Strategic Bombing Survey: The Effects of the Atomic Bombings of Hiroshima and Nagasaki |pages=9, 36 |date=19 June 1946 |url=http://www.trumanlibrary.org/whistlestop/study_collections/bomb/large/documents/pdfs/65.pdf |access-date=15 March 2009 |archive-date=31 January 2012 |archive-url=https://web.archive.org/web/20120131042336/http://www.trumanlibrary.org/whistlestop/study_collections/bomb/large/documents/pdfs/65.pdf |url-status=dead }}</ref><ref>{{cite web |url=http://www.readthespirit.com/ourvalues/life-arises-from-hiroshima-legacy-of-slavery-still-haunts-japan/ |title=Life Arises from Hiroshima: Legacy of slavery still haunts Japan |publisher=Our Values |first=Daniel |last=Buttry |access-date= 15 June 2016}}</ref><ref>{{cite web |url=http://www.hiroshimacommittee.org/Facts_NagasakiAndHiroshimaBombing.htm |title=Hiroshima and Nagasaki Bombing – Facts about the Atomic Bomb |publisher=Hiroshimacommittee.org |access-date=11 August 2013}}</ref>

[[File:Atomic bombing of Japan.jpg|thumb|left|The mushroom clouds of the atomic attacks on [[Hiroshima]], Japan, 6 August 1945 (left) and [[Nagasaki]], Japan, 9 August 1945 (right)|alt=Two mushroom clouds rise vertically.]]
On the morning of 9 August 1945, the ''[[Bockscar]]'',<!-- yes, it is "Bockscar" not "Bock's Car". This is ''not'' a typo! --> a second B-29 piloted by the 393d Bombardment Squadron's commander, Major [[Charles W. Sweeney]], lifted off with a Fat Man on board. This time, Ashworth served as weaponeer and Kokura was the primary target. When they reached Kokura, they found cloud cover had obscured the city, prohibiting the visual attack required by orders. After three runs and with fuel running low, they headed for the secondary target, Nagasaki. Ashworth decided that a radar approach would be used if the target was obscured, but a last-minute break in the clouds over Nagasaki allowed a visual approach as ordered. The Fat Man was dropped over the city's industrial valley midway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works in the north. The resulting explosion had a blast yield equivalent to 21 kilotons of TNT, roughly the same as the Trinity blast, but was confined to the [[Urakami]] Valley, and a major portion of the city, including the city center, was protected by the intervening hills. About 44% of the city was destroyed, and estimates of casualties range from 40,000 to 80,000 people killed and at least 60,000 injured.<ref>{{harvnb|Sklar|1984|pp=22–29}}</ref> Overall, an estimated 35,000–40,000 people were killed and 60,000 injured.<ref>{{harvnb|Groves|1962|pp=343–346}}.</ref><ref name="Hoddeson et al., pp. 396-397">{{harvnb|Hoddeson|Henriksen|Meade|Westfall|1993|pp=396–397}}</ref><ref name="casualties" />

Groves expected to have another atomic bomb ready for use on 19 August, with three more in September and a further three in October.<ref name="Briefing book-HullSeeman">{{cite web |title= Telephone conversation transcript, General Hull and Colonel Seeman (13 August 45) |publisher=George Washington University |date= 13 August 1945 |work=National Security Archive Electronic Briefing Book No. 162 |url= http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB162/72.pdf |access-date=23 January 2024}}</ref> Two more Fat Man assemblies were readied, and scheduled to leave [[Kirtland Air Force Base|Kirtland Field]] for Tinian on 11 and 14 August.<ref name="Hoddeson et al., pp. 396-397" /> At Los Alamos, technicians worked 24 hours straight to cast [[Demon core|another plutonium core]].<ref>{{cite web |url=http://manhattanprojectvoices.org/oral-histories/lawrence-litzs-interview-2012 |title=Lawrence Litz's Interview (2012) |publisher=Manhattan Project Voices |access-date=27 February 2015}}</ref> Although cast, it still needed to be pressed and coated, which would take until 16 August.<ref>{{cite web |url=http://blog.nuclearsecrecy.com/2013/08/16/the-third-cores-revenge/ |title=The Third Core's Revenge |publisher=Restricted Data |first=Alex |last=Wellerstein |author-link=Alex Wellerstein |date=16 August 2013 |access-date=27 February 2015}}</ref> It could therefore have been ready for use on 19 August.

On 10 August, Truman was informed that another bomb was being prepared. He ordered that no additional atomic bombs could be used without his express authority. According to [[Henry A. Wallace]], Truman told his cabinet that "the thought of wiping out another 100,000 people was too horrible. He didn't like the idea of killing, as he said, 'all those kids.'"<ref>{{harvnb|Wallace|1973|p=474}}</ref> Groves suspended the third core's shipment on 13 August.<ref name="Eclipsed by Hiroshima and Nagasaki">{{cite journal |title=Eclipsed by Hiroshima and Nagasaki: Early Thinking about Tactical Nuclear Weapons |first=Barton J. |last=Bernstein |author-link=Barton Bernstein |journal=[[International Security]] |issn=0162-2889 |volume=15 |issue=4 |date=Spring 1991 |pages=149–173 |jstor=2539014 }}</ref>

On 11 August, Groves phoned Warren with orders to organize a survey team to report on the damage and radioactivity at Hiroshima and Nagasaki as soon as the war ended. A party equipped with portable Geiger counters arrived in Hiroshima on 8 September headed by Farrell and Warren, with Japanese Rear Admiral Masao Tsuzuki, who acted as a translator. They remained in Hiroshima until 14 September and then surveyed Nagasaki from 19 September to 8 October.<ref>{{harvnb|Ahnfeldt|1966|pp=886–889}}.</ref> This and other scientific missions to Japan provided valuable data on the effects of the atomic bomb, and led to the creation of the [[Atomic Bomb Casualty Commission]].<ref>{{harvnb|Home|Low|1993|p=537}}.</ref>

In anticipation of the bombings, Groves had commissioned physicist [[Henry DeWolf Smyth]] to prepare a sanitized technical history of the project for public consumption. The idea of releasing such information freely was controversial; the decision to do so was made by Truman personally. The "[[Smyth Report]]" was released to the public on 12 August 1945.<ref>{{harvnb|Groves|1962|pp=348–362}}.</ref>

[[Surrender of Japan|Japan announced its surrender]] on 15 August.<ref>{{cite web|url=http://www.airforcemag.com/MagazineArchive/Pages/2012/August%202012/0812keeper.aspx |title=Hirohito's "Jewel Voice Broadcast" |work=Air Force Magazine |date=August 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130910212019/http://www.airforcemag.com/MagazineArchive/Pages/2012/August%202012/0812keeper.aspx |archive-date=10 September 2013}}</ref> The necessity of the bombings became a [[debate over the atomic bombings of Hiroshima and Nagasaki|subject of controversy among historians]]. Some questioned whether "atomic diplomacy" would have attained the same goals, and the relative weight that the bombs and the [[Soviet–Japanese War (1945)|Soviet declaration of war]] had on the Japanese willingness to surrender.<ref name="Briefing book">{{cite web |last=Burr|first=William|title= The Atomic Bomb and the End of World War II, A Collection of Primary Sources |publisher=George Washington University |date= 13 August 1945 |work=National Security Archive Electronic Briefing Book No. 162 |url= http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB162/|access-date=23 January 2024}}</ref> The [[Franck Report]] was the most notable effort pushing for a demonstration but was turned down by the Interim Committee's scientific panel.<ref>{{harvnb|Frisch|1970|pp=107–115}}.</ref> The [[Szilárd petition]], drafted in July 1945 and signed by dozens of scientists working on the Manhattan Project, was a late attempt at warning Truman about his responsibility in using such weapons.<ref>{{harvnb|Hewlett|Anderson|1962|pp=399–400}}.</ref><ref>{{cite web |url=http://www.trumanlibrary.org/whistlestop/study_collections/bomb/large/documents/index.php?documentdate=17%20July%201945&documentid=79&studycollectionid=abomb&pagenumber=1 |title=Petition to the President of the United States, 17 July 1945. Miscellaneous Historical Documents Collection |publisher=[[Harry S. Truman Presidential Library and Museum]] |access-date=20 October 2012 |archive-date=18 May 2015 |archive-url=https://web.archive.org/web/20150518092746/http://www.trumanlibrary.org/whistlestop/study_collections/bomb/large/documents/index.php?documentdate=17%20July%201945&documentid=79&studycollectionid=abomb&pagenumber=1 |url-status=dead }}</ref>