A 50-year-old compromise that helped pull the world back from the brink of nuclear disaster now faces an uncertain future (as does the world).

The Treaty on the Non-Proliferation of Nuclear Weapons (NPT), signed in 1968 by the United States, Russia and other major world powers, stipulated that countries with nuclear weapons would take steps to reduce their stockpiles, and those without wouldn't attempt to acquire any.

It was a last ditch effort to stem the spread of nuclear weapons technology and reduce the risk of catastrophic nuclear war, particularly between the U.S. and the Soviet Union.

As our latest Above the Noise video points out, the treaty didn't stop proliferation altogether, but it did help dramatically slow down the nuclear arms race of the Cold War.

As a result, 16 nations agreed to abandon their budding nuclear programs. Nearly every nation in the world has now signed on to it (with a handful of notable exceptions). And while Russian and the U.S. still posess the vast majority of the world's nuclear weapons, the total number of warheads worldwide has dropped sharply: there are roughly 15,000 today, down from around 70,000 in the 1980s. Only nine nations are currently known to have them.

But with U.S.-Russian tensions again on the rise, and both of its hawkish leaders increasingly determined to rebuild their nuclear arsenals, the NPT faces its biggest challenge yet. That’s particularly worrisome given the pace of nuclear weapons development in North Korea and Iran, two of the countries that are not part of the deal and who both pose some degree of threat to the U.S.

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Explore this collection of multimedia resources produced by the Council on Foreign Relations and MediaStorm, to learn more about the history of the NPT and where it may be headed. It includes a series of interactive timelines and a map -- View a full-screen version of the interactive here. Below that is a nuts-and-bolts rundown of the NPT and how it works, based on an analysis by the Nuclear Threat Initiative.

Who's involved (and who isn't)?

- There are currently 190 state parties to the NPT, making it the most widely adhered-to arms control treaty in history.

- The NPT designates five parties as nuclear-weapon states (NWS): China, France, the Soviet Union, the United Kingdom, and the United States. All five detonated a nuclear device before January 1, 1967. The 185 other signatories are classified as non-nuclear-weapon states (NNWS). The NPT is effectively a “grand bargain” between the nuclear “haves” and “have-nots.”

- There are only four states that never signed the treaty: India, Israel, Pakistan, and newly independent South Sudan. The first three states all have nuclear weapons, but because they did not detonate a nuclear explosive device before January 1, 1967, they are not technically considered Nuclear Weapons States under the NPT. Joining the treaty would require them to eliminate their nuclear arsenals. South Africa underwent this process in 1991, when it relinquished its nuclear weapons and joined the NPT.
- North Korea withdrew from the NPT in Jan. 2003, the only nation to walk away from the treaty.

What was the NPT created to do?

- The treaty aims to prevent the spread of nuclear weapons to additional countries while ensuring that non-nuclear weapon states have access to peaceful nuclear technology.

- The NPT has three “pillars” or core objectives: disarmament (reducing stockpiles), nonproliferation, and peaceful uses of nuclear technology.

- The treaty’s ultimate goal is the complete elimination of nuclear weapons.

- As part of the treaty, the five nuclear states agree to not transfer nuclear weapons to non-nuclear states or encourage them to acquire these weapons.
- The non-nuclear signatories agree to not build, acquire, possess, or seek to obtain nuclear weapons or receive transfers of nuclear weapons or any other nuclear explosive devices from anyone; they can still develop peaceful nuclear technology, but must agree to international inspections to verify that nuclear material is not used to manufacture weapons.

How is the treaty maintained and enforced?

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