The Able Archer 83 Sourcebook
President's Foreign Intelligence Advisory Board
2015
1983–1990
A retrospective assessment concluding the 1983 NATO command exercise brought the superpowers 'inadvertently' close to nuclear war because Soviet leadership believed the drill was cover for a real first strike.
Why it was classified
It documented catastrophic gaps in U.S. understanding of Soviet threat perception and named intelligence sources still active.
Why it matters
It is the clearest official admission that the Cold War's most dangerous moment after Cuba happened without either side intending it.