Here's another extraordinary document release from Nate Jones of the National Security Archive at George Washington University. His research details, for the first time publicly, the NATO nuclear command post exercise called Able Archer, which was the culmination of a months-long effort to test NATO ground and air warfighting capabilities in Europe. Jones' work makes it clear that the Soviets were alarmed when the U.S. physically transferred more than 10,000 troops to Europe as part of the exercise. From a military standpoint, practicing rapid pre-deployment makes sense. But if your enemy is already interpreting your moves as the precursor to a first strike, it can be quite dangerous. Add to that the nuclear component, which involved actual nuclear aircraft, practice alerts, practice code validations and more.

As Jones notes, one of the after-action reports includes this "startling" observation:

The after-action report includes one startling observation: "The presence of the SAC ADVON [an advance echelon vanguard], especially in large numbers for an exercise of this nature, raises a sensitive, political issue concerning the role of the B-52. One may see an implication or make the inference that if B-52 aircraft are present in a nuclear scenario exercise, are they being used to perform strike missions? Numerous times during the exercise the word "strike" was used in reference to B-52 sorties. While this is an obvious slip of the tongue and was quickly corrected, in most cases, it does serve to fuel any inference should a remark be made in a nonsecure environment. A large, if not fully manned, ADVON team which would be required to properly support ABLE ARCHER, being deployed to the many locations would only again give rise to speculation about the B-52 role."

There's still some debate about how scared the Soviets truly were, but we do know that Ronald Reagan came to believe, after Able Archer and a few other events, that he could no longer act passively with regards to non-proliferation. The policy, he wrote in his diary in early 1984, was too important to be left to the Pentagon. Only a president could save the world.