For nearly 20 years, the secret code to authorize launching U.S. nuclear missiles, and starting World War III, was terrifyingly simple and even noted down on a checklist. From 1962, when John F Kennedy instituted PAL encoding on nuclear weapons, until 1977, the combination to fire the devastating missiles at the height of the Cold War was just 00000000. This was chosen by Strategic Air Command in an effort to make the weapons as quick and as easy to launch as possible.
The US military put such an emphasis on a rapid response to an attack on American soil, that to minimize any foreseeable delay in launching a nuclear missile, for nearly two decades they intentionally set the launch codes at every silo in the US to 8 zeroes.
The Permissive Action Link (PAL) is a security device for nuclear weapons that it is supposed to prevent unauthorized arming or detonation of the nuclear weapon. JFK signed the National Security Action Memorandum 160 in 1962 that required all nuclear missiles to be fitted with a PAL system.
But nuclear experts claim the military was worried about the possibility of command centers or communication lines being destroyed in real nuclear war, stopping soldiers getting the codes or authorization to launch missiles when they were actually needed. So they simply left the security code for the weapons as eight zeros, getting around the security safeguards.
For around 20 years, the Strategic Air Command went out of their way to make launching a nuclear missile as easy, and quick, as possible. To be fair, they had their reasons, such as the fact that the soldiers in the silos in the case of a real nuclear war may have needed to be able to launch the missiles without being able to contact anyone on the outside. That said, their actions were in direct violation of the orders of the Commander-in-Chief, the President of the United States, during a time of extreme nuclear tension. Further, not activating this safeguard and lax security ensured that with very little planning, someone with three friends who had a mind to, could have started World War III.