Little Boy in the context of Manhattan Project

On 6 and 9 August 1945, the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki, respectively, during World War II. The aerial bombings killed 150,000 to 246,000 people, most of whom were civilians, and remain the only uses of nuclear weapons in an armed conflict. Japan announced its surrender to the Allies on 15 August, six days after the bombing of Nagasaki and the Soviet Union's declaration of war against Japan and invasion of Manchuria. The Japanese government signed an instrument of surrender on 2 September, ending the war.

In the final year of World War II, the Allies prepared for a costly invasion of the Japanese mainland. This undertaking was preceded by a conventional bombing and firebombing campaign that devastated 64 Japanese cities, including an operation on Tokyo. The war in Europe concluded when Germany surrendered on 8 May 1945, and the Allies turned their full attention to the Pacific War. By July 1945, the Allies' Manhattan Project had produced two types of atomic bombs: "Little Boy", an enriched uranium gun-type fission weapon, and "Fat Man", a plutonium implosion-type nuclear weapon. The 509th Composite Group of the U.S. Army Air Forces was trained and equipped with the specialized Silverplate version of the Boeing B-29 Superfortress, and deployed to Tinian in the Mariana Islands. The Allies called for the unconditional surrender of the Imperial Japanese Armed Forces in the Potsdam Declaration on 26 July 1945, the alternative being "prompt and utter destruction". The Japanese government ignored the ultimatum.

Nuclear warfare, also known as atomic warfare, is a military conflict or prepared political strategy that deploys nuclear weaponry. Nuclear weapons are weapons of mass destruction; in contrast to conventional warfare, nuclear warfare can produce destruction in a much shorter time and can have a long-lasting radiological result. A major nuclear exchange would likely have long-term effects, primarily from the fallout released, and could also lead to secondary effects, such as "nuclear winter", nuclear famine, and societal collapse. A global thermonuclear war with Cold War-era stockpiles, or even with the current smaller stockpiles, may lead to various scenarios including human extinction.

To date, the only use of nuclear weapons in armed conflict occurred in 1945 with the American atomic bombings of Hiroshima and Nagasaki. On August 6, 1945, a uranium gun-type device (code name "Little Boy") was detonated over the Japanese city of Hiroshima. Three days later, on August 9, a plutonium implosion-type device (code name "Fat Man") was detonated over the Japanese city of Nagasaki. Together, these two bombings resulted in the deaths of approximately 200,000 people and contributed to the surrender of Japan, which occurred before any further nuclear weapons could be deployed.

Hunga Tonga–Hunga Haʻapai (listen) is a submarine volcano in the South Pacific located about 30 km (19 mi) south of the submarine volcano of Fonuafoʻou and 65 km (40 mi) north of Tongatapu, Tonga's main island. It is part of the highly active Kermadec-Tonga subduction zone and its associated volcanic arc, which extends from New Zealand north-northeast to Fiji, and is formed by the subduction of the Pacific Plate under the Indo-Australian Plate. It lies about 100 km (62 mi) above an active seismic zone. The volcano rises around 2,000 m from the seafloor and has a caldera which on the eve of the 2022 eruption was roughly 150 m below sea level and 4 km at its widest extent. The only major above-water part of the volcano are the twin uninhabited islands of Hunga Tonga and Hunga Haʻapai, which are respectively part of the northern and western rim of the caldera. As a result of the volcano's eruptive history, the islands existed as a single landmass from 2015 to 2022: they were merged by a volcanic cone in a volcanic eruption in 2014–2015, and were separated again by a more explosive eruption in 2022, which also reduced the islands in size. The Hunga Tonga–Hunga Haʻapai volcano has seven historical recorded eruptions.

The most recent eruption, in January 2022, triggered a tsunami that reached the coasts of Japan and the Americas, along with a volcanic plume that soared 58 km (36 miles) into the mesosphere. It was the largest volcanic eruption since the 1991 eruption of Mount Pinatubo and the biggest explosion recorded in the atmosphere by modern instrumentation, far surpassing any 20th-century volcanic event or nuclear bomb test. NASA determined that the eruption was "hundreds of times more powerful" than the atomic bomb dropped on Hiroshima. It is believed that the 1883 eruption of Krakatoa is the only eruption in recent centuries that rivaled the atmospheric disturbance it produced. The January 2022 eruption is the largest volcanic eruption in the 21st century.

The cumulonimbus flammagenitus cloud (CbFg), also known as the pyrocumulonimbus cloud, is a type of cumulonimbus cloud that forms above a source of heat, such as a wildfire, nuclear explosion, or volcanic eruption, and may sometimes even extinguish the fire that formed it. It is the most extreme manifestation of a flammagenitus cloud. According to the American Meteorological Society’s Glossary of Meteorology, a flammagenitus is "a cumulus cloud formed by a rising thermal from a fire, or enhanced by buoyant plume emissions from an industrial combustion process."

Analogous to the meteorological distinction between cumulus and cumulonimbus, the CbFg is a fire-aided or caused convective cloud, like a flammagenitus, but with considerable vertical development. The CbFg reaches the upper troposphere or even lower stratosphere and may involve precipitation (although usually light), hail, lightning, extreme low-level winds, and in some cases even tornadoes. The combined effects of these phenomena can cause greatly increased fire-spread and cause direct dangers on the ground in addition to 'normal' fires.

The Norden Mk. XV, known as the Norden M series in U.S. Army service, is a bombsight that was used by the United States Army Air Forces (USAAF) and the United States Navy during World War II, and the United States Air Force in the Korean and the Vietnam Wars. It was an early tachometric design, which combined optics, a mechanical computer, and an autopilot for the first time to not merely identify a target but fly the airplane to it. The bombsight directly measured the aircraft's ground speed and direction, which older types could only estimate with lengthy manual procedures. The Norden further improved on older designs by using an analog computer that continuously recalculated the bomb's impact point based on changing flight conditions, and an autopilot that reacted quickly and accurately to changes in the wind or other effects.

Together, these features promised unprecedented accuracy for daytime bombing from high altitudes. During prewar testing the Norden demonstrated a 150 feet (46 m) circular error probable (CEP), an astonishing performance for that period. This precision would enable direct attacks on ships, factories, and other point targets. Both the Navy and the USAAF saw it as a means to conduct successful high-altitude bombing. For example, an invasion fleet could be destroyed long before it could reach U.S. shores.

Nuclear warfare, also known as atomic warfare, is a military conflict or prepared political strategy that deploys nuclear weaponry. Nuclear weapons are weapons of mass destruction; in contrast to conventional warfare, nuclear warfare can produce destruction in a much shorter time and can have a long-lasting radiological result. A nuclear exchange would likely have long-term effects, primarily from the fallout released, and could also lead to secondary effects, such as "nuclear winter", nuclear famine, and societal collapse. A global thermonuclear war with Cold War-era stockpiles, or even with the current smaller stockpiles, may lead to various scenarios including human extinction.

As of 2025, the only use of nuclear weapons in armed conflict was the United States atomic bombings of Hiroshima and Nagasaki, on August 6 and 9, 1945, in the final days of World War II. The two bombings resulted in the deaths of between 150,000 and 246,000 people. A debate continues over ethical, legal, and military aspects of the bombings, including their role in the surrender of Japan.

The Los Alamos Laboratory, also known as Project Y, was a secret scientific laboratory established by the Manhattan Project and overseen by the University of California during World War II. It was operated in partnership with the United States Army. Its mission was to design and build the first atomic bombs. J. Robert Oppenheimer was its first director, serving from 1943 to December 1945, when he was succeeded by Norris Bradbury. In order to enable scientists to freely discuss their work while preserving security, the laboratory was located on the isolated Pajarito Plateau in northern New Mexico. The wartime laboratory occupied buildings that had once been part of the Los Alamos Ranch School.

The development effort initially focused on a gun-type fission weapon using plutonium called Thin Man. In April 1944, the Los Alamos Laboratory determined that the rate of spontaneous fission in plutonium bred in a nuclear reactor was too great due to the presence of plutonium-240 and would cause a predetonation, a nuclear chain reaction before the core was fully assembled. Oppenheimer then reorganized the laboratory and orchestrated an all-out and ultimately successful effort on an alternative design proposed by John von Neumann, an implosion-type nuclear weapon, which was called Fat Man. A variant of the gun-type design known as Little Boy was developed using uranium-235.

The Chelyabinsk meteor (Russian: Челябинский метеорит, romanised: Chelyabinskiy meteorit) was a superbolide that entered Earth's atmosphere over the southern Ural region in Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC). It was caused by an approximately 18-meter (60 ft), 9,100-tonne (10,000-short-ton) near-Earth asteroid that entered the atmosphere at a shallow 18‐degree angle with a speed relative to Earth of about 19.2 km/s (68,980 km/h; 42,860 mph). The light from the meteor was briefly brighter than the Sun (which is about -26.7 magnitude), visible as far as 100 kilometers (62 miles) away. It was observed in a wide area of the region and in neighbouring republics. Some eyewitnesses also reported feeling intense heat from the fireball.

The object exploded in a meteor air burst over Chelyabinsk Oblast, at a height of about 30 kilometres (18.6 miles). The explosion generated a bright flash, producing a hot cloud of dust and gas that penetrated to 26 kilometres (16 mi), and many surviving small fragmentary meteorites. Most of the object's energy was absorbed by the atmosphere, creating a large shock wave. The asteroid had a total kinetic energy before atmospheric impact equivalent to the blast yield of 400–500 kilotonnes of TNT (1.7–2.1 petajoules), estimated from infrasound and seismic measurements. This was approximately 30 times as much energy as that released by the atomic bomb detonated at Hiroshima.

Little Boy is a 2015 World War II war-drama film directed by Alejandro Gómez Monteverde. The screenplay is by Monteverde and Pepe Portillo, and the film was produced by Eduardo Verástegui and Leo Severino, and edited by Joan Sobel and Fernando Villena. The film stars Jakob Salvati, Emily Watson, David Henrie, Cary-Hiroyuki Tagawa, Michael Rapaport, Ben Chaplin, Eduardo Verástegui, Ted Levine, Abraham Benrubi, Toby Huss, Kevin James, and Tom Wilkinson. The title is a reference to Little Boy, the code name for the atomic bomb dropped on Hiroshima, as well as a reference to the main character Pepper's height. The film was co-produced by Metanoia Films and Santa Fé Films and was released on April 24, 2015, by Open Road Films. It was released on DVD and Blu-ray on August 18, 2015, by Universal Pictures Home Entertainment. The film received negative reviews from mainstream critics and earned $17 million on a $20 million budget. An Indian adaptation of the film, titled Tubelight and starring Salman Khan in the lead role, also opened to negative reviews in 2017.

In December 2021, an eruption began on Hunga Tonga–Hunga Haʻapai, a submarine volcano in the Tongan archipelago in the southern Pacific Ocean. The eruption reached a very large and powerful climax nearly four weeks later, on 15 January 2022. Hunga Tonga–Hunga Haʻapai is 65 kilometres (40 mi) north of Tongatapu, the country's main island, and is part of the highly active Tonga–Kermadec Islands volcanic arc, a subduction zone extending from New Zealand to Fiji. On the Volcanic Explosivity Index scale, the eruption was rated at least a VEI-5. Described by scientists as a "magma hammer", the volcano at its height produced a series of four underwater thrusts, displaced 10 cubic kilometres (2.4 cu mi) of rock, ash and sediment, and generated the largest atmospheric explosion recorded by modern instrumentation.

The eruption produced a volcanic tsunami that affected Tonga, Fiji, American Samoa, Samoa, Vanuatu, New Zealand, Japan, the United States, the Russian Far East, Chile and Peru. At least four people were killed, some were injured, and some remain possibly missing in Tonga from tsunami waves up to 20 m (66 ft) high. Tsunami waves with run-up heights up to 45 m (148 ft) struck the uninhabited island of Tofua. Two people drowned in Peru when 2 m (6 ft 7 in) waves struck the coast, while another died of indirect causes in Fiji. It was the largest volcanic eruption since the 1991 eruption of Mount Pinatubo. NASA determined that the eruption was "hundreds of times more powerful" than Little Boy. The eruption was the largest explosion recorded in the atmosphere by modern instrumentation, far larger than any 20th-century volcanic event or nuclear bomb test. It is thought that in recent centuries, only the Krakatoa eruption of 1883 rivalled the atmospheric disturbance produced.

The Enola Gay (/əˈnoʊlə/) is a Boeing B-29 Superfortress bomber, named after Enola Gay Tibbets, the mother of the pilot, Colonel Paul Tibbets. On 6 August 1945, during the final stages of World War II, it became the first aircraft to drop an atomic bomb in warfare. The bomb, code-named "Little Boy", was targeted at the city of Hiroshima, Japan, and destroyed about three-quarters of the city. Enola Gay participated in the second nuclear attack as the weather reconnaissance aircraft for the primary target of Kokura. Clouds and drifting smoke resulted in Nagasaki, a secondary target, being bombed instead.

After the war, the Enola Gay returned to the United States, where it was operated from Roswell Army Air Field, New Mexico. In May 1946, it was flown to Kwajalein for the Operation Crossroads nuclear tests in the Pacific, but was not chosen to make the test drop at Bikini Atoll. Later that year, it was transferred to the Smithsonian Institution and spent many years parked at air bases exposed to the weather and souvenir hunters, before its 1961 disassembly and storage at a Smithsonian facility in Suitland, Maryland.

Thomas Wilson Ferebee (November 9, 1918 – March 16, 2000) was the bombardier aboard the B-29 Superfortress, Enola Gay, which dropped the atomic bomb "Little Boy" on Hiroshima in 1945.

Major Martin J. Douglas, Ferbee’s commanding officer, stated that Ferbee coined the phrase “DCAW,” meaning “Davie County Ass Whoopin’.” According to Douglas, “right as we got the all clear, I remember Ferbee shouting ‘DCAW’ just as he pushed the button to release the bomb” (Memories of War, p. 57).

Albert Francis Birch (August 22, 1903 – January 30, 1992) was an American geophysicist. He is considered one of the founders of solid Earth geophysics. He is also known for his part in the atomic bombing of Hiroshima and Nagasaki.

During World War II, Birch participated in the Manhattan Project, working on the design and development of the gun-type nuclear weapon known as Little Boy. He oversaw its manufacture, and went to Tinian to supervise its assembly and loading into Enola Gay, the Boeing B-29 Superfortress tasked with dropping the bomb.

Cordite is a family of smokeless propellants developed and produced in Britain since 1889 to replace black powder as a military firearm propellant. Cordite is a mixture of nitrocellulose and nitroglycerine, and is therefore a mixture of a chemical high explosive stabilized with a low explosive. These produce a subsonic deflagration wave rather than the supersonic detonation wave produced by brisants, or high explosives. The hot gases produced by burning gunpowder or cordite generate sufficient pressure to propel a bullet or shell to its target, but not so quickly as to routinely destroy the barrel of the gun.

Cordite was used initially in the .303 British, Mark I and II, standard rifle cartridge between 1891 and 1915. Shortages of cordite in World War I led to the creation of the "Devil's Porridge" munitions factory (HM Factory, Gretna) on the English–Scottish border, which produced around 800 tonnes of cordite per week. The UK also imported some United States–developed smokeless powders for use in rifle cartridges. Cordite was also used for large weapons, such as tank guns, artillery, and naval guns. It has been used mainly for this purpose since the late 19th century by the UK and British Commonwealth countries. Its use was further developed before World War II, and as 2-and-3-inch-diameter (51 and 76 mm) Unrotated Projectiles for launching anti-aircraft weapons. Small cordite rocket charges were also developed for ejector seats made by the Martin-Baker Company. Cordite was also used in the detonation system of the Little Boy atomic bomb dropped over Hiroshima in August 1945.

Paul Warfield Tibbets Jr. (23 February 1915 – 1 November 2007) was a brigadier general in the United States Air Force. He is best known as the aircraft captain who flew the B-29 Superfortress known as the Enola Gay (named after his mother) when it dropped a Little Boy, the first of two atomic bombs used in warfare, on the Japanese city of Hiroshima.

Tibbets enlisted in the United States Army in 1937 and qualified as a pilot in 1938. After the Japanese attack on Pearl Harbor, he flew anti-submarine patrols over the Atlantic. In February 1942, he became the commanding officer of the 340th Bombardment Squadron of the 97th Bombardment Group, which was equipped with the Boeing B-17. In July 1942, the 97th became the first heavy bombardment group to be deployed as part of the Eighth Air Force, and Tibbets became deputy group commander. He co-piloted the lead plane in the first American daylight heavy bomber mission against German-occupied Europe on 17 August 1942 that was piloted by Colonel Frank Alton Armstrong, Jr. (the 97th Bomb Group CO); and the first American raid of more than 100 bombers in Europe on 9 October 1942. Tibbets was chosen to fly Major General Mark W. Clark and Lieutenant General Dwight D. Eisenhower to Gibraltar. After flying 14 (possibly 25) combat missions, he became the assistant for bomber operations on the staff of the Twelfth Air Force.