For the better part of 20 years, all of the nuclear missiles in silos all over the US had their launch codes set to a combination of eight zeros. OMG!

To give you an idea of how secure the PAL system was at this time, bypassing one was once described as being about as complex as performing a tonsillectomy while entering the patient from the wrong end. This system was supposed to be essentially hot-wire proof, making sure only people with the correct codes could activate the nuclear weapons and launch the missiles.

However, though the devices were supposed to be fitted on every nuclear missile after JFK issued his memorandum, the military continually dragged its heels on the matter. In fact, it was noted that a full 20 years after JFK had order PALs be fitted to every nuclear device, half of the missiles in Europe were still protected by simple mechanical locks. Most that did have the new system in place weren't even activated until 1977.

Those in the U.S. that had been fitted with the devices, such as ones in the Minuteman Silos, were installed under the close scrutiny of Robert McNamara, JFK's Secretary of Defence. However, The Strategic Air Command greatly resented McNamara's presence and almost as soon as he left, the code to launch the missile's, all 50 of them, was set to 00000000.