Yesterday, the Obama Administration released the total number of nuclear warheads in the U.S. stockpile, a number that had been classified for decades  . Nonproliferation experts hailed the move as a key step toward openness and reduction of the stockpile.
"This puts a lot of pressure on the Russians to cough up some numbers," says Hans Kristensen of the Federation of American Scientists in Washington, D.C. The nuclear superpowers have cut their stockpiles without disclosing the total number of weapons, but he says that the smaller the stockpiles—and the bigger the focus on weapons not deployed—the more important it is for both sides to know the real totals. The U.S. arsenal contains 5113 warheads, of which 1968 are strategic warheads deployed on long-range bombers or missiles. The rest are tactical weapons planned for battlefield use.
Kristensen deserves congratulations himself: he had estimated  the top secret number at 5200. "Not bad for [predicting] a state secret," he said today. His estimate was derived using information from Freedom of Information Act requests, formal declassifications of documents, newspaper stories, and leaks, and he says it suggests that other states surely could do the same arithmetic. "There's been an enormous number of god-knows how many hints, sources, and information. But if it was possible for nuclear geeks like us to get so close, then I'm sure that our adversaries could know it, too."
The effort to count the weapons in the arsenal began in the 1970s at the Natural Resources Defense Council in Washington, D.C., said Kristensen, who has helmed the effort for the past decade or so. But there's still more to go. The United States has yet to say how many of the 5113 weapons are actually deployed or reveal the balance between strategic weapons and tactical bombs, which can be delivered by fighter jet or sea-launched cruise missiles. In addition, the government won't say how many intact weapons have been retired from the stockpile but have yet to be dismantled.
Kristensen estimates that number at 4000, putting the total number of U.S. nukes at about 9000. And the government has never revealed how many plutonium "pits," which are the key element of nuclear warheads, it has in storage. Those triggers could be made into weapons quickly if the need arose. The U.S. stockpile is believed to have been as large as roughly 37,000 weapons in the 1970s.