A note,  most of this information is interesting, but I find it hard to hear any meaningful military communications,
I guess if you listen LONG AND HARD you will find something,  good luck,
Military Long Range Aeronautical Frequencies
U.S. ARMED FORCES GLOBAL HIGH FREQUENCY SYSTEM IS NOW CALLED
The High Frequency Global Communications System (HF-GCS).
The High Frequency Global Communications System  is a network of
single side band shortwave transmitters of the United States Air Force
which is used to communicate with aircraft in flight, ground stations
and some United States Navy surface assets. All worldwide receiving and
transmitting sites in the HF-GCS system are remotely controlled from Andrews AFB.
PUBLISHED FREQUENCY LISTING - HFGCS stations operate on “core" frequencies
to provide increased "Global" coverage. The published frequency listing does not reflect
complete system frequency authorizations. These published frequencies will be used
for initial contact, EAM broadcasts, and short-term phone patch and message delivery.
Other extended or special services will be moved to each station’s available "discrete" frequencies.
You may hear highly encrypted or coded voice transmissions at times that make no sense
whatsoever. Just be patient. Military and national security at work!
HF-GCS stations tend to operate in the aviation bands clustered around 5, 8 and 11/12 MHz,
although other frequencies are in use.
The primary HF-GCS voice frequencies are.
4724.0 KHz, 6739.0 KHz, 8992.0 KHz, 11175.0 KHz, 13200.0 KHz and 15016.0 KHz
Primary HFGCS Frequencies 24 Hours:   8992 and 11175
Back up HFGCS Frequencies Day:        13200  15016
Back up HFGCS Frequencies Night:      4724  6739
In addition to the HF-GCS, U.S. aircraft frequently use Military Affiliate Radio System (MARS)
HF stations (13927.0 KHz) and Canadian Forces HF stations (11232.0 KHz) to relay messages.
Although transmissions are often single sideband, the use of the ALE , a type of digital transmission mode,  is more and more common.
4.709	Sigonella
4.724	Andrews, Ascension, Elmendorf, Guam, Hickam, Lejes, Offutt, Salinas, Thule, Yokota
4.742
6.712	Andrews, Ascension, Guam, Lajes
6.724	Sigonella
6.739	Ascension, Elmendorf, Guam, Hickam, Salinas, Offutt, Thule, Yokota
8.992	Andrews, Ascension, Elmendorf, Guam, Hickam, Offutt, Salinas, Thule, Yokota
9.007	Sigonella
9.025	Lejes
10.780	AF Eastern Test Range (Backup for Ascension), Cape Canaveral, Antigua, Ascension, Maui
11.175	Andrews, Ascension, Elmendorf, Guam, Hickam, Salinas, Offutt, Thule, Yokota
11.181	Lajes
11.244
11.271	Andrews, Ascension, Elmendorf, Guam, Hickam, Lejes, Offutt, Salinas, Thule, Yokota
13.200
13.212	Lajes
15.016	Andrews, Ascension, Elmendorf, Guam, Hickam, Lajes, Offutt, Salinas, Thule, Yokota
15.038	Sigonella
20.390	AF Eastern Test Range (Backup for Ascension), Cape Canaveral, Antigua, Ascension, Maui