After the U.S. and Russia (and to an extent Britain) had built their first nuclear weapons stockpile, they engaged in a series of public very public tests. These were as much military — to find out the destructive capabilities of the ever-larger ordinances — as scientific — to find out the radiation’s duration and effects. Mostly they were done for show, to impress and intimidate the enemy. By the late 1950s, the scientific aspect gained precedence, and scientists began to find traces of radioactivity in food from around the region. The nuclear tests needed to stop.

On this day, August 5, in 1963, Secretary of State Dean Rusk for the United States, Foreign Minister Andrei Gromyko for the Soviet Union, and Lord Home for Great Britain signed an agreement to cease any further nuclear testing, whether on land, under water, or in space.

Negotiations for a mutually acceptable agreement went on for the better part of a decade. The U.S. and Russia had a three-year moratorium on testing from 1958 to 1961. The USSR proposed at one point a complete ban on all nuclear testing, but the idea was rejected. After the expiration of the moratorium the USSR announced they would resume testing, exploding some 31 weapons over the course of the next three months — including a 58 megaton one, the largest nuclear bomb to ever be detonated, with 4,000 times the power of the Hiroshima bomb.