On Tuesday, August 6, Japan observed the 68th anniversary of the moment when “Little Boy” dropped out of the skies from the bomber bay of a B-29 dubbed the Enola Gay onto the unsuspecting city of Hiroshima. Today, Friday, August 9, is the 68th anniversary of the morning when “Fat Man” dropped out of Bockscar onto the city of Nagasaki.

Despite their nicknames, there was nothing frivolous about either bomb. They were the world’s first two atomic weapons unleashed on a “live target,” and they killed nearly 250,000 people – at least half of them within seconds of their mushroom-clouded moments of impact. Fortunately, from that day until this, they also are the only two nuclear devices ever unleashed against live targets.

The thinking behind creating and then using such weapons of mass destruction was that once the world realized their horrific possibilities, war would never again be an option.

Instead, we live in fear of “dirty bombs” that can be carried in briefcases; of clothing that can be soaked in liquids that become explosive when dry (supposedly just developed for al Qaeda in Yemen); of pocket-sized laser pens aimed from the ground that can cause jet liners to crash by blinding their pilots.

Nuclear weapons can serve as deterrents. No one doubts that. That is why the United States built up its nuclear arsenal. And we recall the dark humor of Tom Lehrer in his song Who’s Next: “Israel’s getting tense, wants one in self-defense. ‘The Lord’s our shepherd,’ says the psalm, but just in case, we better get a bomb.'”

Not everyone, however, sees nuclear weapons as for deterrence only. Iran’s nuclear program remains a serious concern, and one we are not convinced is being taken seriously enough now that Mahmoud Ahmadinejad is no longer its president. North Korea’s motives for building a nuclear arsenal are also of great concern, especially because it has no qualms about sharing its arsenal with terrorists and rogue states.

It is 68 years since August 6, 1945; 68 years after the world first arrived at the brink of nuclear annihilation. If we want it never to fall off that cliff, we must be more aggressive in keeping those who might use WMDs from ever getting them.