This is a super-geeky military communications history talk - a perfect fit for this blog. If you have the time to watch or listen you will find this a fascinating first-person account of communications activities from Vietnam all the way up to the first Gulf War. This chat with retired Army Lieutenant Colonel David Fiedler is both interesting and illustrative. It's not just about HF communications, but about how the Army handled communications requirements and challenges overall during the Vietnam and post-Vietnam era.
LTC Fiedler provides a fascinating overview of Army-level and theater-level communications decision making, including some not-so-complimentary comments about Signal Corps senior leadership and officer training. I also enjoyed his comments about how Army Special Forces handled its tactical communications challenges by bypassing 'Big Signal' rules and going their own route with radio development. Many of the radios that emerged from that development effort were groundbreaking HF manpack systems that are hot collector items today.
One last observation. It's clear from listening to LTC Fiedler that as far back as the early 60's the Army Signal Corps had blinders on in regards to HF-based long-haul comms systems. In Vietnam this led to a critical communications gap, when VHF line-of-sight system failed, particularly in heavy jungle canopy. It seems the Army Signal Corps forgot that it's a combat support branch - the communications mission exist to support the warfighter, and is not an end unto itself.