Fat Man in the context of "Trinity (nuclear test)"

The RDS-1 (Russian: РДС-1), also known as Izdeliye 501 (Device 501) and First Lightning (Russian: Пе́рвая мо́лния, romanized: Pyérvaya mólniya, IPA: [ˈpʲervəjə ˈmolnʲɪjə]), was the first test of a Soviet nuclear bomb. It was roughly based on the American design, Fat Man, and the United States assigned it the code-name Joe-1, in reference to Joseph Stalin.

It was detonated on 29 August 1949 at 7:00 a.m. MSK (UTC+03:00), at the Semipalatinsk Test Site in the Kazakh Soviet Socialist Republic.

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.

Little Boy was a type of atomic bomb created by the Manhattan Project during World War II. The name is also often used to describe the specific bomb (L-11) used in the bombing of the Japanese city of Hiroshima by the Boeing B-29 Superfortress Enola Gay on 6 August 1945, making it the first nuclear weapon used in warfare, and the second nuclear explosion in history, after the Trinity nuclear test. It exploded with an energy of approximately 15 kilotons of TNT (63 TJ) and had an explosion radius of approximately 1.3 kilometres (0.81 mi) which caused widespread death across the city. It was a gun-type fission weapon which used uranium that had been enriched in the isotope uranium-235 to power its explosive reaction.

Little Boy was developed by Lieutenant Commander Francis Birch's group at the Los Alamos Laboratory. It was the successor to a plutonium-fueled gun-type fission design, Thin Man, which was abandoned in 1944 after technical difficulties were discovered. Little Boy used a charge of cordite to fire a hollow cylinder (the "bullet") of highly enriched uranium through an artillery gun barrel into a solid cylinder (the "target") of the same material. The design was highly inefficient: the weapon used on Hiroshima contained 64 kilograms (141 lb) of uranium, but less than a kilogram underwent nuclear fission. Unlike the implosion design developed for the Trinity test and the Fat Man bomb design that was used against Nagasaki, which required sophisticated coordination of shaped explosive charges, the simpler but inefficient gun-type design was considered almost certain to work, and was never tested prior to its use at Hiroshima.

Bockscar, sometimes called Bock's Car, is the United States Army Air Forces Boeing B-29 Superfortress bomber that dropped a Fat Man atomic bomb over the Japanese city of Nagasaki during World War II in the second – and most recent – nuclear attack in history. One of 15 Silverplate B-29s used by the 509th, Bockscar was built at the Glenn L. Martin Bomber Plant at Bellevue, Nebraska, at what is now Offutt Air Force Base, and delivered to the United States Army Air Forces on 19 March 1945. It was assigned to the 393rd Bombardment Squadron, 509th Composite Group to Wendover Army Air Field, Utah, in April and was named after captain Frederick C. Bock.

Bockscar was used in 13 training and practice missions from Tinian, and three combat missions in which it dropped pumpkin bombs on industrial targets in Japan. On 9 August 1945, Bockscar, piloted by the 393rd Bombardment Squadron's commander, Major Charles W. Sweeney, dropped a Fat Man nuclear bomb with a blast yield equivalent to 21 kilotonnes of TNT (88 TJ) over the city of Nagasaki. The explosion destroyed about 44% of the city, killed 35,000 people, and injured 60,000 people.