The agreement prevented the spread of nuclear weapons to countries that didn’t already have them by 1967. Countries with nuclear weapons, like the U.S. and the U.K., agreed to end their nuclear arms race and work toward eventual disarmament, meaning the destruction of all nuclear weapons.

This landmark agreement laid the groundwork for agreements between the U.S. and the Soviet Union to further reduce their nuclear weapons and their delivery systems. It also stopped other countries from developing and testing nuclear weapons until the end of the Cold War.

Israel, India and Pakistan never joined the agreement due to regional security concerns. They all now possess nuclear weapons. North Korea withdrew from the agreement and developed nuclear weapons.

There have been major achievements in preventing countries from gaining nuclear weapons and dramatically reducing nuclear weapons stockpiles since the Cold War.

The global nuclear stockpile has been reduced by 82% since 1986, from a peak of 70,300, with nearly all of the reductions in the U.S. and Russia, who held the largest stockpiles at the time.

Globally there are now around 12,700 nuclear weapons, with about 90% held by Russia and the U.S. – or between 5,000 to 6,000 weapons each.

Several other countries have nuclear weapons, and most of them have a few hundred weapons each, including the United Kingdom, France and China – though China has been building up its nuclear stockpile. Newer nuclear countries like India, Pakistan and Israel have around 100 each, while North Korea has around 20.

Starting in the late 1960s, countries agreed to more than a dozen legally binding agreements, or treaties, that limited new countries from getting nuclear weapons and prohibited nuclear weapons testing, among other measures.

But they have not reduced the number of nuclear weapons with short-range missiles.

No agreements cover these weapons, which could also cause widespread destruction and deaths.

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