During Able Archer 83, the Soviet Union allegedly got close to launching a first strike against the US because <i>they</i> feared an imminent US attack because of what they picked up of the exercise.<p>Advertising to the world that you have a firm policy against nuclear attacks other than in very limited, clearly defined scenarios puts you at risk of the other side decides it is ok to strike you for their own gains, but it also protects you against potential adversaries who have no designs on you but who you might inadvertently scare.<p>Able Archer 83, and the realisation that it appears to have genuinely terrified the Soviet leadership is often credited with changing Reagans course and making him determined to sit down with the Soviet leadership.