The USSR detonated the Tsar Bomba, a 27-ton hydrogen bomb, above the Arctic test site of Novaya Zemlya on October 30, 1961. Yielding roughly 50 megatons—about 3,300 times the force of the Hiroshima bomb—it remains the most powerful explosive device ever detonated by humans. The test was a Cold War show of force under Khrushchev, demonstrating Soviet capability even as the weapon was too large and unwieldy for practical military deployment.
The bomb was so massive that the Tu-95 bomber carrying it had to be specially modified, stripped of its bomb bay doors, and painted with reflective white paint to survive the flash. It was dropped by parachute to give the plane time to fly roughly 45 kilometers away before detonation, and the crew was told they had only a 50 percent chance of surviving the blast wave. The fireball reached nearly 5 miles wide and the mushroom cloud rose about 40 miles high, visible from over 600 miles away, while the shockwave circled the Earth three times.
Windows shattered hundreds of miles from ground zero, and the blast registered on seismographs worldwide. Nikita Khrushchev had ordered the test scaled up from an original 100-megaton design, reportedly to intimidate the West during the tense months following the Berlin Wall's construction, though scientists had already halved the yield by replacing a uranium tamper with lead to limit fallout. No weapon of comparable size has been tested since; the Tsar Bomba stands as the ceiling of thermonuclear brinkmanship, a demonstration whose destructive potential was almost entirely theoretical because such a device could never be practically used.
Key people: Nikita Khrushchev, Andrei Sakharov