I was a Naval Officer at the very tail end of John Walker's career (about the time when the ring was busted). Access to the information that he provided the USSR was likely as damaging or more than any other information compromised in US history, either from within or without the military.
He ultimately leakef information that potentially could have provided the Soviets with the capability to successfully launch a nuclear first strike against the USA, it don't get any worse than that.
He ultimately leakef information that potentially could have provided the Soviets with the capability to successfully launch a nuclear first strike against the USA, it don't get any worse than that.