There are a number of good YouTube videos on the resurgence of HF communications in the US Army that have been released in the last decade, and I've touched on the topic in this blog. For me this is a fascinating topic - I'm very much an 'everything old is new again' kind of guy.
This presentation by Colonel Stephen Hamilton from the Army Cyber Institute is probably the best single presentation on the topic. If you've followed this topic at all in the past few years you've seen a lot of this material, but this is probably the best compilation of all the information, and COL Hamilton clearly has mastery of the topic.
The presentation was hosted by The Radio Club of America. Highly recommended, and definitely worth tagging as a favorite in your YouTube account.