The United States tested the world's first thermonuclear device, codenamed Ivy Mike, at Enewetak Atoll in the Pacific, escalating the Cold War arms race to a terrifying new level.
The blast yielded roughly 10.4 megatons — more than 700 times the power of the bomb dropped on Hiroshima — and vaporised the entire island where it was detonated. The test confirmed the viability of fusion weapons and triggered the Soviet Union to accelerate its own thermonuclear programme within a year.
