President Obama sure is spending a lot of time worrying about nuclear weapons this week. Today’s Nuclear Security Summit – a meeting of over 40 world leaders in Washington, D.C. – caps seven days of highly publicized events on nuclear security.

The attention lavished on atomic weapons feels almost anachronistic, invoking a Cold War-era standoff that now seems so distant. Twenty-five years ago, I was a third grader at St. Joan of Arc in Chagrin Falls, Ohio. Once a month, Ms. Elliot would trot my class into the hallway where we’d kneel down and clasp our hands behind our necks. This wasn’t some strange Catholic school ritual – we were “protecting” ourselves from a Soviet nuclear attack.

While I realize now that this defensive maneuver wouldn’t have kept me safe from a direct hit on the jungle gym, the looming threat of a mushroom cloud over the American Midwest felt real.

It doesn’t today. The end of the Cold War, years of American military dominance and improving, if occasionally frustrating, relations with Moscow have effectively banished the threat of mutually assured destruction. Beyond Russia, it’s nearly impossible to imagine China, perhaps the United States’ “near-peer” military competitor but also its financial Siamese twin, launching its nuclear weapons.

But nuclear security must be important – just glance at Obama’s schedule. Before signing the New START accord with Russian President Dmitri Medvedev last Thursday, his administration released its Nuclear Posture Review, an important document that redefines the way America will use the 1550 deployed warheads New START permits. And today the president is convening the summit of world leaders in Washington, D.C.

It’s not only this week. These events are part of a yearlong effort that began last April when President Obama spoke about his vision of a world without nuclear weapons.

It’s a long-term goal to be sure — Obama has been clear that America would retain its arsenal as long as others did. But it’s hardly a liberal fantasy — conservative icons like former Secretaries of State Henry Kissinger and George Shultz have joined forces with mainstream Democrats like former Senator Sam Nunn and Defense Secretary Bill Perry to promote a nuclear-free world.

They’re following the legacy of Ronald Reagan, who nearly signed on to sweeping nuclear restrictions with Mikhail Gorbachev in Iceland in 1986, and George H.W. Bush, who signed the START treaty in 1991.

So with no Cold War threat, what’s the urgency? Why is the president wasting time negotiating with countries that wouldn’t dare attack us anyway?

Here’s why — it’s not state-sponsored atomic destruction that’s the threat. It’s the al-Qaeda operative with a nuclear suitcase. That sounds crazy, right? Then again, we never could have imagined that three airliners could bring down the Twin Towers and slam into the Pentagon. President Obama realizes that a nuclear arsenal in the hands of nation-states still poses a threat, albeit from stateless ones.

How, then, does a stuffy gathering of world leaders at a conference center in Washington, D.C. keep the bomb away from a small-fry terrorist? First, curbing nuclear proliferation depends on the large nuclear powers — U.S., Russia, China, U.K. and France — showing a serious and sustained effort towards nuclear disarmament that convinces the smaller nuclear powers — India, Pakistan and Israel — and nuclear weapons aspirants — North Korea and Iran — to feel comfortable without them. That dialogue needs to start on a big stage, particularly for American allies India and Pakistan, who may want to do the right thing but happen to be mortal enemies.

What’s more, it’s the North Koreas, Irans and Pakistans of the world that stand the greatest chance of selling nuclear technology to the black market’s highest bidder. Getting those countries to swear off nuclear weapons planning is critical. Just ask A.Q. Khan — he might be a hero as the father of the Pakistani A-bomb, but he has also sold nuclear secrets to Iran and North Korea in the 1980s and 1990s for tens of millions of dollars.

We need nation-states to control their nuclear scientists, and getting everyone on the same page — as Obama’s doing — is the first step to achieving that goal.

We are long-removed from cowering in the hallway of my Catholic school in Ohio, but that doesn’t mean the nuclear threat died with the Cold War. It has simply changed. That’s why the Obama administration is spending so much time yanking America’s nuclear security policy into the 21st century.

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