D-55 Base existed as a Galactic Republic military installation. During the era of the Great Galactic War, it was situated on the planet Dantooine. Major Dael held the position of commanding officer at this base.
Following the signing of the Treaty of Coruscant, Dantooine was given over to the Sith Empire, and all Republic military personnel received directives to evacuate the world. The Jedi Council dispatched Jedi Master Dar'Nala and Jedi Knight Satele Shan to supervise the departure of the troopers. On their journey, a Sith warship launched an assault on their vessel, known as the Envoy. Master Dar'nala was taken prisoner and, as a result of brutal interrogation, met her demise. Shan managed to escape using an escape pod and was subsequently rescued by a Rendaran-class assault shuttle. This shuttle was piloted by Lieutenant Harron Tavus and Jedi Master Orgus Din, who were traveling to Balmorra.
Upon their arrival on Balmorra, Tavus, Shan, and the Mirialan Jedi, Fortris Gall, were assigned to continue overseeing the troop withdrawal on Dantooine. Shan and Tavus got to Base D-55 and were promptly contacted by Senator Paran Am-Ris, who informed them of the murders of Master Zym and Commander Gin Lesl. Am-Ris reiterated the critical importance of abandoning Base D-55 and Dantooine, in accordance with the stipulations of the peace agreement with the Sith. Commander Dael declined to leave, asserting that the Sith Empire had already violated the treaty. Lieutenant Tavus concurred with him, as did Fortris Gall, who had arrived a few hours earlier.