Halting Iran's progress toward a bomb will require the United States to make credible promises and credible threats simultaneously -- an exceedingly difficult trick to pull off.

Graham Allison ("The Cuban Missile Crisis at 50," July/August 2012) seems to believe that U.S. President John F. Kennedy's handling of the Cuban missile crisis was an unalloyed success.

A nuclear-armed Iran would not make the Middle East more secure, argues Colin Kahl; it would yield more terrorism and pose a risk of a nuclear exchange.

U.S. and Israeli officials have declared that a nuclear-armed Iran is a uniquely terrifying prospect, even an existential threat. In fact, by creating a more durable balance of military power in the Middle East, a nuclear Iran would yield more stability, not less.

When it comes to Iran's nuclear program, then, the United States and its allies should get out of the way and let Iran's worst enemies -- its own leaders -- gum up the process on their own.

Is reducing the world's nuclear arsenals to zero possible, or even desirable?

How would the Israeli defense establishment respond if Iran went nuclear?

All previous attempts at total nuclear disarmament have failed, as strategic logic and state interest have prevailed over wishful thinking. A similar fate awaits Global Zero, the newest disarmament movement, for similar reasons.

It is unclear how a nuclear-armed Iran would weigh the costs, benefits, and risks of brinkmanship, meaning that it could be difficult to deter Tehran from attacking the United States' interests or partners in the region.

For decades, Israel has maintained an "opaque" nuclear posture -- neither confirming nor denying that it possesses nuclear weapons. The time has come for Israel to reconsider the policy of nuclear ambiguity.

Is it too late to convince North Korea and Iran to dismantle their nuclear programs?

If the Obama administration has any hope of reducing the world's nuclear arsenals, the U.S. government will have to assuage the fears of nonnuclear states, diminish the prestige of nuclear weapons, and address the risk of proliferation posed by civilian nuclear energy programs.

Why North Korea will not change.

The outcome of the North Korean nuclear saga has been held up as an example of the Bush administration defying its bellicose reputation and using multilateralism and diplomacy to defuse a crisis. But in fact, the story is one of extremely poor policymaking and a persistent failure to devise a coherent strategy -- with the result that North Korea has managed to dramatically expand its nuclear capability.

The Bush administration has adopted a misguided and dangerous nuclear posture. Instead of recycling antiquated doctrines and building a new generation of warheads, the United States should drastically reduce its nuclear arsenal, strengthen the international nonproliferation regime, and move toward the eventual elimination of nuclear weapons.

Carter's update to his July/August 2006 essay "America's New Strategic Partner?"