Americans have feared nuclear weapons for more than a half century. Presidents have often used that fear to justify their policies and actions.

John F. Kennedy tried to scare voters with a fictitious “missile gap” between the United States and Russia in his 1960 election campaign. Mr. Kennedy later employed nuclear fear to try to persuade Americans to build bomb shelters in their back yards and basements – actually a device to show the Soviet Union that the United States could launch a first-strike nuclear attack without fear of a successful counterattack. Ronald Reagan used the same fear in the 1970s to justify his Star Wars plan for protection against enemy missiles, for the same purpose. George W. Bush has used this fear to justify his plans for a limited missile-defense system and his recent order to deploy the still unproved system.

That same fear figures in Mr. Bush’s current drive to prepare the American people and U.S. allies for a possible war against Iraq and pressuring North Korea. He keeps warning, quite accurately, that Saddam Hussein, despite his denials, appears determined to develop nuclear weapons. And that North Korea has openly begun a two-track effort to produce nuclear bombs while further improving the missiles to deliver them. Yet, for all the warnings and fears, no nuclear weapon has been fired in anger since the United States bombed Hiroshima and Nagasaki in 1944 to help bring a victorious end to World War II.

A good question is: Why not? When only the United States and the Soviet Union had nuclear weapons, each aimed them at the other but each knew that if it fired first the other side would retaliate and both would suffer devastating death and destruction. Strategists called the standoff an avoidance of “mutually assured destruction,” or MAD.

Those who favor a U.S. war against Iraq and possibly a military strike against North Korea dispute the MAD concept. But just as it worked throughout the Cold War, it has worked thus far with Iraq and North Korea. Here’s why: If either fired the weapons at the United States or one of its allies, the United States would certainly crush them with furious counter blow. Neither Saddam nor North Korea’s Kim Jong Il is suicidal, so neither would fire first unless he already faced defeat and destruction. Mere threats to use nuclear weapons would be hollow for the same reason.

The Bush administration war hawks have one further argument. They insist that Saddam and al-Qaida are in cahoots and that Saddam might furnish nuclear weapons to the al-Qaida terrorists. This reasoning fails on two counts. First, Saddam is the sort of secular Arab leader that Osama bin Laden hates and threatens, so Saddam would hardly want to arm him or his terrorist network with nukes. Second, try as they may, the hawks have failed to show any serious connection between Saddam and al-Qaida. The story of a supposed meeting between Mohamed Atta, the leader of the Sept. 11 hijackers, and an Iraqi spy in Prague has fallen flat. The U.S. CIA and most allied intelligence agencies scoff at talk of a Saddam-al-Qaida alliance. Defense Secretary Donald Rumsfeld has set up a Pentagon intelligence branch to try to find a link between the few, but so far to no avail.

Sure, it’s a dangerous world we live in. But there is no need to panic and accept war as inevitable.