The world's patchwork of nuclear nonproliferation treaties and agreements hasn't yet been ripped apart – but it's under strain as never before.
North Korea's apparent test of a nuclear device this week is but the latest shock to an international regimen that for the most part has been remarkably successful since its construction at the dawn of the atomic age, more than 40 years ago.
The challenge now may be to rally the globe's big powers into a more solid League Against the Spread of Nukes. Potential proliferators such as Iran may be likely to forge ahead unless they see that the US, China, and Russia are willing to forgo business deals, or pay more for oil, to help control nuclear weapons.
"You want to show the Iranians that we're actually willing to take some risks on our own to act against nuclear weapons," says George Perkovich, a nuclear strategy and nonproliferation expert at the Carnegie Endowment for International Peace in Washington.
The main element of what experts call the world's nonproliferation architecture is the Nuclear Non-Proliferation Treaty (NPT), which was opened for signatures on July 1, 1968, in New York. It's augmented by more informal agreements, such as the Nuclear Suppliers Group, and various country-to-country pacts and regional nuclear-free zones.
In general, it has been successful. North Korea is the only country that has acquired nuclear weapons after signing the NPT. (Pyongyang withdrew from the treaty in 2003.) India and Pakistan have developed an atomic arsenal in recent decades, and Israel is thought to have one, but none of them signed the NPT to begin with.
The number of nations with declared weapons, officially seven (not including North Korea), is far smaller than US intelligence reports of the 1960s predicted. Most important, no atomic weapon has been detonated in anger since the United States dropped the Hiroshima and Nagasaki bombs in 1945.
Today this nonuse seems natural, considering the terrible nature of the weapons, but it wasn't foreordained. Back in the early 1960s, when ads for bomb shelters were a common sight, many experts thought it was only a matter of time until someone dropped a bomb.
Thomas Schelling, a renowned strategic deterrence theorist, considers nuclear nonuse such a remarkable development that he made it the theme of his acceptance address before the Swedish Academy when he won the Nobel Prize in economics in 2005.
In the 1960s, "If I had said, 'Oh, come on, nobody is going to use nuclear weapons for the next 40 years,' everybody would have thought I was out of my mind," said Mr. Schelling at a Council on Foreign Relations event earlier this year.
But now, the global status quo on nuclear weapons is being shaken as never before by the twin threats of Iran and North Korea.
Iran, an NPT signatory, has in essence been caught in the act of violating the pact, via revelations of covert fissile-material programs.
"If Iran can look us in the eyes and say, 'We're going ahead,' what does that say for the system?" says Mr. Perkovich of Carnegie.
North Korea, meanwhile, has a long history of exporting its weapons systems to unsavory customers with cash. Preventing Pyongyang from proliferating nuclear devices to terrorists may now be one of the biggest security challenges faced by the US and the rest of the developed world.
The US can't win a war on nuclear terrorism alone, notes Graham Allison, director of the Belfer Center for Science and International Affairs at Harvard's John F. Kennedy School of Government in Cambridge, Mass.
He recommends declaration of a GAANT – Global Alliance Against Nuclear Terrorism.
"Establishment of a Global Alliance Against Nuclear Terrorism could help us overcome the psychological barriers to sustained, focused action," writes Dr. Allison in the latest issue of the Bulletin of the Atomic Scientists.
Among other things, such an organization could establish a more robust regimen to control trade in nuclear materials and know-how, including some sort of enforcement mechanism, writes Allison.
It could also provide a formal infrastructure for such efforts as joint exercises in tracking hypothetical nuclear terrorists.
To get the international cooperation needed to stop covert trade in fissile materials, the US might also consider developing something that Robert Gallucci, dean of Georgetown University's Edmund Walsh School of Foreign Service, dubs "expanded deterrence."
Fissile material, like a person, has unique identifying characteristics. A US crash program might develop the capability to identify where any fissile material came from.
The US could then announce that it would treat a nuclear attack on the US as an attack by both the perpetrator and the country from which the weapon's fissile material was obtained – meaning US weapons might attack both targets in retaliation.
"It may be that, by threatening unacceptable consequences, we can deter that which we cannot physically prevent," writes Mr. Gallucci in the Annals of the American Academy of Political and Social Science.