First casualty in Vietnam was an as Air Force MI Sergeant.
A significant number of MI slots are off the books.
From the article about first casualty in VN ... " ... Fifty years ago, 25-year-old [Tom] Davis, a Tennessee Tech engineering student, joined the Army and went to Vietnam on a secret mission.
Davis was in Vietnam intercepting communist radio signals and alerting the south Vietnamese so they could target and destroy those operations. ..."
I believe he was ASA (Army Security Agency).
L.W.