The first ready-to-use thermonuclear bomb ' RDS-6s' ('Joe 4') was tested on August 12, 1953, in the Soviet Union. The first test of a hydrogen bomb prototype was the ' Ivy Mike' nuclear test in 1952, conducted by the United States. The modern design of all thermonuclear weapons in the United States is known as the Teller-Ulam design for its two chief contributors, Edward Teller and Stanislaw Ulam, who developed it in 1951 for the U.S., with certain concepts developed with the contribution of John von Neumann. The concept of the thermonuclear weapon was first developed and used in 1952 and has since been used in most of the world's nuclear weapons.

The fusion stage in such weapons is required to efficiently cause the large quantities of fission characteristic of most thermonuclear weapons. It is colloquially referred to as a hydrogen bomb or H-bomb because it employs hydrogen fusion, though in most applications the majority of its destructive energy comes from uranium fission, not hydrogen fusion alone. This results in a greatly increased explosive power. The compressed secondary is heated from within by a second fission explosion.Ī thermonuclear weapon is a nuclear weapon design that uses the heat generated by a fission bomb to compress and ignite a nuclear fusion stage.

Radiation from a primary fission bomb compresses a secondary section containing both fission and fusion fuel. The basics of the Teller–Ulam design for a thermonuclear weapon.

Fission device