Overview of Department of Defense Use of the Electromagnetic Spectrum [Updated March 18, 2021] [open pdf - 2MB]
From the Summary: "Communication using the electromagnetic spectrum ('the spectrum') enables a number of modern military capabilities. The Department of Defense (DOD) uses electromagnetic radiation to enable military communications, navigation, radar, nonintrusive inspection of aircraft, and other equipment. [...] The U.S. government manages access to and use of spectrum. As the nation continues to experience significant growth in commercial wireless services (e.g., mobile phones, mobile applications, video streaming, Wi-Fi), demand for spectrum has increased. Congress has enacted policies to make additional spectrum available for commercial use, in some cases reallocating spectrum from federal agency use to commercial use. As Congress considers policies that reallocate spectrum from DOD to commercial use, it may consider the following issues:  'Interoperability' (i.e., the ability of one radio or computer system to talk to another). [...]  'DOD's ability to keep pace with technological advances by potential adversaries.' [...]  'The private sector's increasing interest in using frequencies traditionally reserved for the military.' [...]  Spectrum sharing. [...]  The interagency process for spectrum allocation. [...]  Anticipating future spectrum needs for both commercial and military users."
CRS Report for Congress, R46564
Congressional Research Service: https://crsreports.congress.gov/