Donald Trump spirals downward. As long as he remains in the White House, we are called upon to do everything in our power to limit the damage he can do. Above all, there is the need to prevent a war of choice to disarm North Korea of its nuclear weapons.

There are many reasons to exercise restraint, along with deterrence, sanctions, and diplomacy. The first may seem quaint to tough-minded analysts and members of Congress: Under international law, the only justification for a preventive war is if an adversary poses an imminent threat of attack. This particular adversary poses a threat of attack only if threatened with attack.

The second relates to the track record of the tough guys. After the extended traumas of Afghanistan and Iraq, another U.S. military campaign must be nearly immaculate in execution and almost immediate in North Korea’s capitulation. Let those who predict this result after cheerleading the war in Iraq come forward and forthrightly say so.

The third reason for restraint relates to the track record of a nation badly wounded after 9/11. A war with North Korea would be the third fought by the United States in just 16 years. The first two continue without end. U.S. expeditionary forces have been through Hell and back, and yet war hawks, having been temporarily foiled by successful diplomacy to strictly limit Iran’s bomb-making capacity, are setting the predicates for another war of choice.

Yes, the threat posed by Kim Jong-un and the North Korean nuclear program is very real. And yes, tougher sanctions against North Korea are needed. But what if sanctions do not succeed in forcing Kim Jong-un to capitulate and give up that which he holds most dear? Then what? Another war with heavy casualties would hand Beijing the keys to Asia and cause far wider ruptures in the NATO alliance. America’s treasury would be deeper in the red and its standing in the world will decline further and faster – even after victory on the battlefield.

There is no justice in another war of choice that results in many thousands of deaths of allied and U.S. soldiers and civilians, as well as the deaths of countless innocents in North Korea. Worse, there is no justice in another war of choice that results in even a single mushroom cloud.

The norm of not using nuclear weapons on battlefields has been accepted and practiced for seven decades since Hiroshima and Nagasaki. This norm is the most important stabilizing factor in a world of growing nuclear dangers. The reappearance of mushroom clouds on battlefields would be devastating enough; they could also prompt renewed nuclear testing by major and regional powers, as well as the shredding of what’s left of treaties to reduce nuclear dangers. Is a seven-decade old norm to be broken because a country with thousands of deliverable nuclear weapons has convinced itself that it cannot deter the use of one or more by North Korea?

Are the methods American Presidents used to prevent the battlefield use of nuclear weapons by paranoid mass murderers like Josef Stalin and Mao Zedong completely useless against the likes of Kim Jong-un? These methods included deterrence, but deterrence alone does not prevent war or reduce nuclear dangers. Deterrence accompanied by wild threats is more dangerous still. Deterrence requires diplomacy and reassurance to reduce nuclear dangers.

Nuclear strategists who seek to “strengthen” deterrence by tailoring weapon effects and yields are living in an unreal world. Safety doesn’t come from smaller mushroom clouds. It comes from the absence of mushroom clouds. No strategic analyst has ever offered a convincing explanation of how nuclear-armed states can succeed at escalation control after engaging in warfare and detonating nuclear weapons.

This doesn’t stop a nuclear competition, because the competitors continue to seek advantage and fear being placed at a disadvantage. This was the treadmill the United States and the Soviet Union were on during the Cold War, until Ronald Reagan and Mikhail Gorbachev decided to get off. There is no safety in repeating what has not worked before. The Cold War nuclear arms race didn’t keep the peace; it endangered it. Nor is escalation control helped by fine-tuning war-fighting capabilities. The surest way to achieve escalation control is to not use nuclear weapons on battlefields.

A third war of choice since 9/11 would be folly. A wiser course would be to rely upon the instruments that have succeeded in preventing mushroom clouds since 1945: a strong military, strong alliances, deterrence, a purposeful military presence in tense regions, and active diplomacy. Diplomacy is the key element missing today.

But here’s the rub: direct diplomacy is unlikely to eliminate that which we most fear. The best achievable outcome may well be the cessation of North Korean testing of nuclear devices and missiles. If this unacceptable to President Trump – if he cannot abide a mutual deterrence relationship with North Korea – then for as long as he is in the White House and Kim Jong Un remains in power, another war on the Korean peninsula will remain possible.

Michael Krepon is co-founder of the Stimson Center.