The PTBT kind of arrived just in time. All of this nuclear stuff was getting out of hand and making the Cold War a round-the-clock nightmare for almost everyone. (We say "almost" because we're accounting for those people who already lived in underground bunkers.)

When the treaty was finally signed on August 5th, 1963, it was a huge victory for anti-nuclear activists, peace workers, and the original parties. The signatures of Rusk, Douglas-Home, and Gromyko made the treaty official, but it didn't formally go into force until several months later. That's because, when it comes to treaties, there are several levels of commitment.

Small Steps

The first level of commitment is the signing stage, which the original parties took care of right away. In the case of the PTBT, this is an example of what is called "signature subject to ratification, acceptance or approval."

This means "[w]here the signature is subject to ratification, acceptance or approval, the signature does not establish the consent to be bound," i.e., it needs another signature to seal the deal, according to the United Nations Treaty Collection Glossary.

This second signature is called "ratification," which is "the international act whereby a state indicates its consent to be bound to a treaty if the parties intended to show their consent by such an act." In some instances, it is called "acceptance or approval," which is essentially the same thing: "[t]he instruments of 'acceptance' or 'approval' of a treaty have the same legal effect as ratification and consequently express the consent of a state to be bound by a treaty." They both function as an oath. Keep your promises! (Source)

In the months following its initial signing, the treaty was ratified by each of the original parties. It went into full effect on October 10th, 1963, and was immediately very popular. Within half a year, 100 nations had signed, and nearly 40 had ratified it. Nations continue to join the treaty to this day—Montenegro just joined in 2017.

Upshots and Misfires

The PTBT had a major impact on slowing the unhinged development of nuclear weapons and resulted in the marked reduction of radiation in the atmosphere that was a result of atmospheric testing.

But it wasn't magic—it didn't cease testing altogether because it still allowed for underground testing, which was argued to be a self-contained and "safer" method. Countries like Russia and the U.S. still conduct underground nuclear tests, sometimes with terrible results. One example of things going horribly awry was the Baneberry incident, in which a radioactive cloud was accidentally released from the testing site below ground, exposing a whole bunch of people to high doses of radiation.

The other thing the PTBT was unable to stop was something called "nuclear proliferation." This is the spread of nuclear weapons technology and materials to an increasingly larger number of governments and other groups.

It was a major concern for the original parties because it both threatened their powerful statuses as world powers and increased the likelihood of nuclear warfare. A whopping nine nations possess nuclear weapons today.

Anti-Nuclear Trendsetting

The PTBT was the first treaty of its kind, and it set the stage for the creation of a variety of related treaties in the following decades:

• Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (1967).
• Treaty on the Non-Proliferation of Nuclear Weapons (1968).
• Anti-Ballistic Missile Treaty (1972).
• Treaty on the Limitation of Underground Nuclear Weapon Tests (1975).

In the 1980s, talks about the Comprehensive Nuclear-Test-Ban Treaty began at the U.N., and as expected, they took forever. Finally, in 1996, the CTBT was signed (technically taking the place of the PTBT), but it hasn't gone into force because it has yet to be ratified by several of the required nations, including the U.S.

The good news? We're making baby steps toward getting rid of nuclear testing. The bad news? We aren't there yet…not by a long shot.