Permissive Action Links, or PALs, are on our nuclear missiles to ensure that no one can, um, shoot 'em just fer fun.

Comes now Monster, in wonkish mode, with a link to a really scary story.

Here's an excerpt:

Last month I asked Robert McNamara, the secretary of defense during the Kennedy and Johnson administrations, what he believed back in the 1960s was the status of technical locks on the Minuteman intercontinental missiles. These long-range nuclear-tipped missiles first came on line during the Cuban missile crisis and grew to a force of 1,000 during the McNamara years — the backbone of the U.S. strategic deterrent through the late 1960s. McNamara replied, in his trade-mark, assertively confident manner that he personally saw to it that these special locks (known to wonks as “Permissive Action Links”) were installed on the Minuteman force, and that he regarded them as essential to strict central control and preventing unauthorized launch.

When the history of the nuclear cold war is finally comprehensively written, this McNamara vignette will be one of a long litany of items pointing to the ignorance of presidents and defense secretaries and other nuclear security officials about the true state of nuclear affairs during their time in the saddle. What I then told McNamara about his vitally important locks elicited this response: “I am shocked, absolutely shocked and outraged. Who the hell authorized that?” What he had just learned from me was that the locks had been installed, but everyone knew the combination.

The Strategic Air Command (SAC) in Omaha quietly decided to set the “locks” to all zeros in order to circumvent this safeguard. During the early to mid-1970s, during my stint as a Minuteman launch officer, they still had not been changed. Our launch checklist in fact instructed us, the firing crew, to double-check the locking panel in our underground launch bunker to ensure that no digits other than zero had been inadvertently dialed into the panel. SAC remained far less concerned about unauthorized launches than about the potential of these safeguards to interfere with the implementation of wartime launch orders. And so the “secret unlock code” during the height of the nuclear crises of the Cold War remained constant at OOOOOOOO.

Breathe deeply. And again. It'll be okay. I hope.