Once secret NSA document rewrites Vietnam War history

Did the NSA lose a treasure trove of top-secret cryptographic equipment and material to the North at the end of the Vietnam war? Investigative journalist and NSA expert James Bamford has said so. But in 2002, official NSA historians refuted that in an internal essay. Of course, this being NSA, the rebuttal was classified.

Now that essay, SIGINT and the Fall of Saigon, April 1975, has been (mostly) declassified in a Mandatory Declassification Review initiated by attorney and journalist Michael Ravnitzky. Here's the NSA's side of the story...