Vietnam Study, Casting Doubts, Remains Secret

By SCOTT SHANE
Published: October 31, 2005

WASHINGTON, Oct. 28 - The National Security Agency has kept secret since 2001 a finding by an agency historian that during the Tonkin Gulf episode, which helped precipitate the Vietnam War, N.S.A. officers deliberately distorted critical intelligence to cover up their mistakes, two people familiar with the historian's work say.