Shot George was the fourth nuclear detonation of Operation Greenhouse, fired on 9 May 1951 from a 61-metre tower on Eberiru Island, Enewetak Atoll. At 225 kilotons it was the largest nuclear explosion ever conducted at that point — a record it held until the Ivy Mike thermonuclear test 17 months later. George was not a weapon test but a thermonuclear physics experiment: a proof of concept for fusion ignition using a fission device configured to direct thermal radiation into a small chamber of cryogenic deuterium-tritium fuel. The fusion yield itself was negligible, but the experiment successfully demonstrated that thermonuclear ignition was achievable and yielded data critical to the development of the hydrogen bomb.