We learn two things: that USAF and USN were out-fought by North Vietnamese fighters over North Viet-Nam, and that SIGINT made a huge difference when it focused on supporting tactical air combat in near real time.
Phi Beta Iota: Intelligence capabilities are like any capability — they can be used for good, or evil. TEARBALL is an inspiring success story. Less inspiring is the fact that NSA lost several cyrpto machines captured in Viet-Nam, and lied to Congress and the White House by omission — NSA knew for years that the Russians were reading most circuits by being able to combine the cyrpto machines captured in Viet-Nam with the key cards turned over by the Falcon and the Snowman. It is this kind of integrity failure that characterizes virtually every aspect of US “secret” intelligence today.