It is obvious that nuclear weapons are incredibly important. Vast sums are spent on them, concerns about their spread—most recently, to North Korea and Iran—dominate headlines, and they could blow up the world in a flash.

And yet. They haven’t been used since World War II. They are purchased, deployed, and discussed on separate tracks from the rest of the foreign policy agenda, and they are largely ignored by nonspecialists, with little apparent consequence.

In fact, nearly three-quarters of a century into the atomic age, it is sobering to consider how little we really know. Do nuclear weapons truly matter, and if so, how and why? Should we worry about them more or less? As the “whiz kids” working under U.S. Secretary of Defense Robert McNamara famously asked, how much is enough?

John Mueller kicks off this issue’s lead package bluntly. For generations, the world has supposedly been on the brink of one nuclear catastrophe or another: “bolts from the blue, accidental wars, lost arms races, proliferation spirals, nuclear terrorism.” He notes: “The common feature among all these disasters is that none of them has ever materialized. Either we are the luckiest people in history or the risks have been overstated.” The policies adopted to ward off those hypothetical disasters, meanwhile, have had terrible consequences. You do the math.

Such complacency is dangerous, counters Nina Tannenwald. Worst-case scenarios may not have materialized, but there have been enough near misses to demonstrate the risks, so why continue to play Russian roulette? U.S. President Barack Obama tried to jump-start a disarmament movement in Prague in 2009, but his efforts were blocked, so the threats remain.

Elbridge Colby agrees about the dangerous complacency, but for the opposite reason. The real risks come from a weakened United States without the capabilities or the will to maintain deterrence in the twenty-first century. Only a modernized U.S. arsenal and an updated American strategy can continue to preserve global peace.

The actual challenge is narrower, says Scott Sagan: what to do when personalist dictatorships, such as North Korea, get the bomb. Careful handling and creative policymaking might contain the situation, but Washington is not providing either.

Caitlin Talmadge’s warning is down-right scary: the United States and China could slip into a nuclear war because of careless strategizing. Better communication would help, but the real challenge is unlocking the escalatory gears inside current war plans.

Olga Oliker, finally, reports that Russia is modernizing its arsenal, but not its basic strategy. Moscow believes that any major war with the United States could result in a massive U.S. nuclear attack, so it wants a powerful retaliatory capacity of its own, to deter an American nuclear first strike.

Let’s hope the risks are as low as Mueller thinks—or that we stay lucky.

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