Operation Ivy 1952

Two tests: Mike (10.4 Mt) and King (500 kt). Mike was the world's first hydrogen bomb — a cryogenic device weighing 82 tons that vaporized the island of Elugelab. King was the largest pure fission bomb ever tested. The Mike shot was kept secret from the American public for years. Yield: 694 Hiroshimas.

Ivy Mike opened the thermonuclear era: within two years both superpowers fielded deliverable hydrogen bombs, and the logic of the arms race shifted from kilotons to megatons.