The US Navy were the largest user of the Gulfstream I in military service. The type entered service in early 1968 as the TC-4C Academe. The main role in a joint US Navy / US Marine Corps was to train A-6 Intruder bombardiers and navigators. These G159s had been produced with the A-6 Intuder's bulbous nose (see pic below) giving them a very unique look. Unsurprisingly, the retirement of the TC-4C coincided with that of the Intruder in 1995. Most of the nine frames ordered ended their careers at AMARG Davis Monthan, Arizona. Only one TC-4C remains on public view, this at the NAS Pensacola museum, Florida.
One Gulfstream I was operated by the US Army but carried a civilian registration and scheme (c/n 002 N40CE). The final US service to operate the G159 were the two US Coast Guard VC-4As which were used for VIP transport and as in the civilian world, these were replaced by a Gulfstream II.
Only one other Gulfstream I saw military service and that was with the Greek Air Force as a VIP transport. Currently preserved at Tatoi airbase, P9 (c/n 120) flew with the Greeks between 1964 - 1995.