Operation Ivy
Ivy Mike thermonuclear device detonated at Elugelab
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Original prompt & settings (JSON) ↗Briefing papers told Eisenhower the result in four words: the island used for the shot 'is missing.'
1 November 1952, 07:14:59.4 — six-tenths of a second early
At 07:14:59.4 local time on 1 November 1952, Joint Task Force 132 detonated the experimental Mike device on Elugelab islet at Enewetak Atoll — firing about 0.6 second early after a power failure aboard the command ship USS Estes.
The 10.4-megaton explosion was the first full-scale test of a staged thermonuclear device. The date carries a calendar quirk: it was still 31 October in Greenwich time, which is why the Department of Energy labels the shot October 31 while operational histories use the local 1 November.
An apparatus, not a deliverable bomb
Mike ran on cryogenic liquid deuterium — a massive experimental installation, not an operationally deliverable weapon. Truman had ordered continued work on thermonuclear weapons in 1950; the Teller–Ulam staging breakthrough later made a full-scale proof test feasible, and Mike demonstrated that concept at megaton scale.
The explosion erased Elugelab, replacing the islet with a submarine crater approximately 1.9 kilometres across.
The pilot who didn't come back
Air Force pilots entered the radioactive cloud to collect debris. On the return flight, Captain Jimmy P. Robinson's F-84G ran out of fuel; he disappeared while attempting to ditch at sea, and later received a posthumous Distinguished Flying Cross.
The collected debris kept giving after the day ended: laboratory analysis of debris collected from the Mike cloud later contributed to the discovery of two previously unknown elements, einsteinium and fermium. Operation Ivy's second shot, King, followed about two weeks later — a separate event, not part of 1 November.
Sources
Researched 23 Aug 2026 6 sources 3 audit passes, 2 issues open
How this was checked
Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →
What the sources leave uncertain
- The local date at Enewetak was November 1, but the detonation occurred at 19:14:59 on October 31 in Greenwich time. This explains why the Department of Energy labels it October 31 while operational histories use November 1.
- Contemporary spellings vary: Enewetak/Eniwetok and Elugelab/Eluklab appear in official records.