Editing Manhattan Project (section)

=== 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>