Abstract: The U.S. Military Health System (MHS) pioneered the use of telehealth in deployed environments in the early 1990s. However, its use in non-deployed environments historically lagged behind that of the Veterans Health Administration (VHA) and comparable large civilian health systems, due to administrative, policy, and other obstacles that slowed or blocked its expansion in the MHS. A report was prepared in December 2016, which summarized past and then-present telehealth initiatives in the MHS; described the obstacles, opportunities, and policy environment; and provided three possible courses of action for expansion of telehealth in deployed and non-deployed settings. Gray literature, peer-reviewed literature, presentations, and direct input were aggregated under the guidance of subject matter experts. Past and then-current efforts demonstrated significant telehealth capability in use and in development for the MHS, mainly in deployed or operational settings. Policy from 2011 to 2017 demonstrated an environment favorable for MHS expansion, while the review of comparable civilian and veterans' healthcare systems showed significant benefits including increased access and lower cost from use of telehealth in non-deployed settings. The 2017 National Defense Authorization Act charged the Secretary of Defense with promoting telehealth usage for the Department of Defense, including provisions for removing obstacles and reporting progress within 3 years. The MHS has the ability to reduce burdensome interstate licensing and privileging requirements, but still requires an increased level of cybersecurity, compared to civilian systems. The benefits of telehealth fit with the MHS Quadruple Aim of improving cost, quality, access, and readiness. Readiness is particularly served by the use of "physician extenders," which allows nurses, physician assistants, medics, and corpsmen to provide hands-on care under remote oversight and to practice at the top of their licenses. Based on this review, three courses of action were recommended: to focus largely on developing telehealth in deployed environments; to maintain focus in deployed environments and increase telehealth development in non-deployed environments to keep pace with the VHA and private sector; or to use lessons learned from military and civilian telehealth initiatives to leapfrog the private sector. This review serves as a snapshot in time of the steps leading to telehealth expansion before 2017, which helped to set the stage for later use of telehealth in behavioral health initiatives and as a response to coronavirus disease 2019. The lessons learned are ongoing and further research is expected to inform additional development of telehealth capability for the MHS.