REUTERS/KCNA Those Americans who may be fearful of North Korea’s verbal threats and its missile-launch preparations should take note: Its leaders have long expressed a fear of an American nuclear attack.

This fear by three successive leaders from the Kim family in Pyongyang helped pushed them to develop atomic bombs. Now the regime’s threat to attack the United States defies the very logic of the nuclear age – namely, that states with nuclear weapons would always act rationally because of the risk of massive retaliation, or “assured destruction.”

As historian Ward Wilson points out in a new book, “Five Myths About Nuclear Weapons,” atomic bombs “were born out of fear, nurtured in and sustained by fear.” Their power to devastate requires a mutual fear to avoid their use.

The current escalation of threats between the US and North Korea illustrates how this reliance on fear can falter. Nations that rely on maximizing fear as a primary tool for defense will find the emotion very difficult to manage in all cases.

The North’s threats, for example, have now led South Korea to consider ending its ban on developing its own nuclear weapons. It is asking for US support to start a nuclear program.

Many in Seoul, South Korea, see the American people as too weary for war and the Obama administration as too eager to reduce the US nuclear arsenal unilaterally. They fear that the American “nuclear umbrella,” which has protected South Korea for 60 years, may no longer be credible enough to deter North Korea from either launching nuclear weapons or using them as blackmail.

For two decades, the US has tried to talk down North Korea from possessing nuclear weapons by offering hope in place of fear. It tried to convince Pyongyang that the US was not a threat while offering its food aid and oil supplies in return for nuclear disarmament. It hasn’t worked, despite some limited help from China.

Similar persuasion is now being tried on Iran: Give up your nuclear ambitions and instead become a regional power through the strength of your economy, ideas, and culture. In other words, replace the fear that looks to nuclear power for comfort and instead build up your nation’s “soft power.”

President Obama, who came into office with the goal of eliminating the world’s nuclear weapons, has had a difficult time making his case. Instead, he has to now send B-2 bombers near North Korea to assure South Korea of the US nuclear umbrella and as a threat to North Korea. The tit-for-tat of fear only keeps rising.

His recent trip to Israel was designed in part to persuade Iran to cease its uranium enrichment. His visit was an attempt to reinforce faith in the US nuclear umbrella for the region, especially Israel. But as with North Korea, the logic of deterrence assumes that the leaders in Iran will be both fearful and rational.

In the past few decades, a dozen countries have given up their nuclear programs or handed over nuclear weapons on their soil. After the breakup of the Soviet Union in 1991, for example,Kazakhstan cooperated with Russia and the US to hand over the weapons in its possession. Most of those nations chose to seek safety in being a nation of peace, goodwill, and prosperity while also relying on an international system that depends to a large degree on the US maintaining it.

And most nations abide by international agreements banning the use of chemical and biological weapons. Fear of those weapons has been largely contained.

Yet as more nations like North Korea obtain nuclear weapons, and as the US struggles to keep a credible nuclear umbrella over its allies from Asia to Europe to the Middle East, the world needs to find a replacement for the current system of maintaining stability based on the mutual fear of nuclear war.

North Korea’s threats show just how urgent that need is.