The United States successfully detonates Ivy Mike, the first thermonuclear device, at the Eniwetok atoll. The explosion had a yield of ten megatons TNT equivalent.

TNT equivalent is a convention for expressing energy, typically used to describe the energy released in an explosion. The tonne of TNT is a unit of energy defined by that convention to be 4.184 gigajoules, which is the approximate energy released in the detonation of a metric ton (1,000 kilograms) of TNT. In other words, for each gram of TNT exploded, 4.184 kilojoules (or 4184 joules) of energy is released.

This convention intends to compare the destructiveness of an event with that of conventional explosive materials, of which TNT is a typical example, although other conventional explosives such as dynamite contain more energy.

Ivy Mike was the codename given to the first full-scale test of a thermonuclear device, in which part of the explosive yield comes from nuclear fusion.

Ivy Mike was detonated on November 1, 1952, by the United States on the island of Elugelab in Enewetak Atoll, in the now independent island nation of the Marshall Islands, as part of Operation Ivy. It was the first full test of the Teller–Ulam design, a staged fusion device.Due to its physical size and fusion fuel type (cryogenic liquid deuterium), the "Mike" device was not suitable for use as a deliverable weapon. It was intended as a "technically conservative" proof of concept experiment to validate the concepts used for multi-megaton detonations.As a result of the collection of samples from the explosion by U.S. Air Force pilots, scientists found traces of the isotopes plutonium-246 and plutonium-244, and confirmed the existence of the predicted but undiscovered elements einsteinium and fermium.