The first full-scale test of a thermonuclear device (known as Mike Shot) was done by the United States in 1952; the concept has since been employed by most of the world's nuclear powers in the design of their weapons. The first test by the Soviet Union of a thermonuclear bomb -- known as "RDS-6s" or "Joe 4" was carried out on August 12, 1953. Although Joe-4 produced a significantly smaller yield than the Mike Shot, this weapon was ready for immediate use and could be delivered by a bomber.

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