On March 1, 1954, the United States attempted something it had never done before: The explosion of a hydrogen bomb in an operation code-named "Castle Bravo."
Unfortunately, the test at Bikini Atoll in the South Pacific didn’t go exactly as planned, making this date something of an infamous anniversary. PBS, in its terrific Secrets of the Dead series, explains what happened:
As soon as the bomb exploded, the test team knew something was wrong. Instead of five megatons, the blast turned out to be 15 megatons. The explosion vaporized three entire coral islands, sending the ash 100,000 feet into the air. It drifted eastward and rained upon hundreds of people living on islands to the north – a poison footprint of 7,000 square miles.
According to the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization, which really could use a more economical name, the botched test gave rise to global criticism of nuclear testing. The organization, which seeks to ban nuclear explosions worldwide, posted a poignant quote from an observer that day:
Approximately five hours after detonation, it began to rain radioactive fallout at Rongelap. Within hours, the atoll was covered with a fine, white, powdered-like substance. No one knew it was radioactive fallout. (…) The children played in the snow. They ate it.
For more on the botched test, watch this declassified U.S. nuclear test film on Operation Castle: