A&Q is a special series that inverts the classic Q&A, taking some of the most frequently posed solutions to pressing matters of policy and exploring their complexity.

Many Americans have probably forgotten about nuclear weapons. But they are, once again, threatening world security. As The New York Times reported recently, major nuclear powers are rebuilding and upgrading their nuclear arsenals. The world is at the brink of a new nuclear arms race that former Secretary of Defense Bill Perry warns “will be at least as expensive as the arms race we had during the Cold War.”

Why? Has the world become more dangerous? And if it has, will upgraded nuclear weapons keep America safer? Even if all of these questions were asked and answered during the Cold War, it is important to examine them again as the U.S. prepares to spend $1 trillion on a new generation of nuclear weapons.

ANSWER

It's a dangerous world out there, and it's getting worse as more and more countries get nuclear weapons. Donald Trump is actually right to say it's essentially a matter of time before places like Japan seek to get their own arsenals as trust in the American nuclear guarantee erodes.

QUESTION

Does Trump have the time arrow pointing in the wrong direction? No nation has begun a nuclear weapon program in this century, and North Korea is the only nation to have tested a nuclear bomb in this century. When John F. Kennedy warned about the threat of nuclear weapons in the hands of countries “large and small, stable and unstable,” he was looking at threat assessments that counted 23 countries with weapon programs or potential weapon programs. Today, there are only nine.

Having just rolled back Iran’s nuclear program, if the world can stop North Korea, we could reasonably be looking at the end of proliferation, the wave of weapon programs that began over 70 years ago following the first nuclear attack, on Hiroshima. While several nations have the technical capability to make nuclear materials and nuclear weapons, there is no other country with a dedicated program like North Korea’s. Our nuclear nightmares could continue to shrink.

ANSWER

That's somewhat comforting. It remains true, though, that the world is a dangerous place. America's nuclear weapons, at least, actually make the world safer by deterring potential conflicts through the threat of massive retaliation.

QUESTION

Has history shown that to be true? Nuclear-armed states are attacked all the time. The U.K.’s nuclear weapons didn’t stop Argentina from attacking the British-held Falkland Islands in 1982. Israel’s nuclear weapons didn’t stop Arab states from attacking that country in 1973. Nor did they deter North Vietnam from fighting the United States. Nuclear-armed India and Pakistan still teeter on the edge of all-out war.

True, the potential for going nuclear may have reduced the risk of a global war between the Soviet Union and the United States, but deterrence almost failed catastrophically several times, including during the Cuban Missile Crisis.

In the real world, those who have had their fingers on the button have taken a different view of nuclear weapons’ security benefits. Colin Powell had 28,000 nuclear weapons under his command as chairman of the Joint Chiefs of Staff. “The one thing I convinced myself after all these years of exposure to the use of nuclear weapons is that they were useless,” he has said. President Ronald Reagan knew that “Everybody would be a loser if there’s a nuclear war.”

Using a nuclear bomb on a non-nuclear armed foe could kill hundreds of thousands of innocent men, women, and children, send shock waves through global security and financial structures, and bring world condemnation on the perpetrator of the catastrophe. Using such a bomb on a nuclear-armed adversary would trigger a devastating nuclear response.

ANSWER

There is no way that treaties, or diplomatic agreements like the Iran deal, can restrict this kind of danger, though. The problem is that the good guys would abide by the restrictions and the bad guys would cheat.

QUESTION

How effective have treaties and other agreements been at limiting nuclear proliferation?

As I’ve argued elsewhere, the nuclear Non-Proliferation Treaty is the most effective security treaty in history. Coupled with positive security guarantees, it provides the diplomatic, political, and legal framework that has helped convince dozens of nations to end nuclear-weapon programs.

Thanks in great part to the treaty and related agreements, the entire southern hemisphere is free of nuclear weapons, including the continents of South America and Africa. States that have cheated, like Iran, pay a heavy penalty or, like North Korea, are ostracized. Only Israel, Pakistan, and India have remained outside this global pact.

ANSWER

But none of this means that we don't need nuclear weapons as the ultimate guarantor of our security—of course they're only for use in emergencies, but emergencies do happen.

QUESTION

Who didn’t cheer when Will Smith saved our planet by flying a nuclear bomb up the belly of the alien mothership in Independence Day? Who wasn’t rooting for Iron Man when he carried a nuclear cruise missile through a wormhole to destroy the alien invaders in The Avengers? Or when military heroes in giant robotic suits used a nuclear weapon to seal the trans-dimensional portal and destroy the monstrous Kaiju in Pacific Rim?

In Hollywood and in the popular imagination, nuclear weapons are the ultimate defense. America invented them, perfected them, and multiplied them until they numbered in the thousands on the country’s planes, ships, subs, and silos. America believes it needs them to defend against enemies known and yet to be known.

It’s a great story. It just isn’t true.

There has not been a military mission that required the use of a nuclear weapon for over 70 years. In those decades, the United States has been in major wars. It has lost major wars. So have America’s allies. Yet neither the president of the United States nor any leader in the eight other nuclear-armed nations has ordered the use of a nuclear bomb.

There is a lot of loose talk from presidential candidates and fringe politicians. But Hollywood had to invent alien monsters to justify the use of these weapons.

ANSWER

I guess that means it’s a good thing Obama has let our nuclear arsenal deteriorate.

QUESTION

Has he? In a speech in Prague in 2009, Obama stated “clearly and with conviction America’s commitment to seek the peace and security of a world without nuclear weapons.” But he coupled that with a pledge to keep America’s nuclear arsenal “safe, secure, and effective.” Obama actually increased spending on nuclear weapons compared to the Bush administration.

This has created a huge problem. As Obama’s arms-control agenda stalled, his spending on weapons contracts soared. He will leave office with some key accomplishments in the area of nonproliferation, most importantly the Iran agreement. But he will also leave behind plans to spend over $1 trillion on new nuclear weapons. Over the next 30 years, the Pentagon wants to replace every Cold War-era nuclear-armed plane, missile, sub, and warhead with a brand-new version, many with new capabilities and even new missions.

This is a recipe for nuclear disaster. Whatever security benefits nuclear weapons may have had during the Cold War, they are now the world’s greatest security risk. Only nuclear weapons have the power to destroy America. This is why Reagan said in 1985, “We seek the total elimination one day of nuclear weapons from the face of the Earth.”

If America wants to continue to cut global arsenals and stop the arrival of new nuclear states, it can’t be building a brand-new nuclear arsenal that will last through the end of this century. It’s like trying to get your kids not to smoke when you have a two-pack-a-day habit.

ANSWER

Okay, but as long as nuclear weapons exist, America will need to keep some.

QUESTION

True, but how many does America need?

The use of one nuclear weapon on one city would unleash a level of destruction not seen since the end of World War II. The use of 10 on 10 cities would be a catastrophe beyond anything in human history. The use of 100 could cause the collapse of civilization as we know it.

America has roughly 7,000 nuclear weapons.

So does Russia. Together, those two countries have almost 95 percent of all the nuclear weapons in the world. France, the U.K., and China have about 200 each. India, Pakistan, and Israel have about 100 each. North Korea has enough material for a dozen or so. This is an insane amount of destruction to keep in fallible human hands.

Here is the good news: Global nuclear arsenals are down from their Cold War peak. Way down. In 1986, there were almost 65,000 nuclear weapons in the world; now there are 15,000.

That is still enough to destroy the world many times over, but the movement over the past 30 years is unmistakably positive.

No one is talking about unilateral disarmament, but joint, verifiable reductions in these bulging arsenals will make the world more secure. Until we kill dangerous new programs, put to rest the nuclear dinosaurs still roaming the earth, and get down to truly low numbers of nuclear weapons, we won’t be safe.

As long as nuclear weapons exist—especially in large numbers in many states—there is the risk of accident, miscalculation, or madness and the chance that a terrorist group could get a nuclear bomb or the material to build one. We can safely go down, step by step, to much lower numbers.

And we can always keep a couple around in case the aliens come calling.

* * *

How exactly America can reduce the nuclear risks it faces may be the toughest issue confronting the next president.

During the four years of his or her term, the president will make 50-year decisions. Does America build new nuclear weapons that will maintain the Cold War arsenals well past the middle of this century, or does it redouble its efforts to reduce and ultimately eliminate nuclear weapons?

For that matter, is it possible to really get rid of all nuclear weapons? Is it possible that nothing terrible will happen if we don’t?

A great deal depends on White House priorities. Will the next U.S. president care as deeply about this issue as Kennedy, Reagan, and Obama did? He or she will have to confront the argument that the world—and the United States specifically—can’t afford to get rid of nuclear weapons. But can it afford to keep them?