It was 74 years ago that the United States became the first and only country ever to use nuclear weapons in war, detonating two bombs over Hiroshima and Nagasaki and ending the Pacific campaign in World War II.

The destructive power of those bombs made nuclear weapons the sine qua non of strategic power, which inevitably led to an arms race and to dangerous proliferation. Today, it is the bad guys such as North Korea, Iran, and terrorist organizations that pose a nuclear threat.

This creates a perilously ironic contrast between past and present. Today we fear that North Korea and Iran might use nukes. We assume that terrorists would. But at one time, the deterrent effect of mutually assured destruction made nuclear weapons the mainstay of peace. Knowing America could turn Russia to ashes meant the Soviet Union never dared to use its vast superiority in conventional weapons to overrun Western Europe.

Ronald Reagan, in his 1984 State of the Union address, said, "A nuclear war cannot be won and must never be fought. The only value in our two nations possessing nuclear weapons is to make sure they will never be used."

This was understood even in pop culture. Joshua, the computer in the 1983 Cold War film, WarGames couldn't "win" a game of global thermonuclear war with itself, concluding, "the only winning move is not to play."

The United States and Russia have 1,600 active deployed strategic nuclear warheads. China, France, and Great Britain also have active warheads. This maintains the motivation to avoid conflict.

Does it also make North Korea and Iran tread carefully when developing and discussing their nuclear capabilities? One can hope.