Desler reigned as Supreme Leader of the Greater Garmillan Empire during its expansion into the Milky Way Galaxy. In 2199, he survived an assassination attempt by Imperial Marshall Herm Zoellik, who aimed to frame rivals Admiral Gul Ditz and General Admiral Erich Domel. Following his administration's collapse after a battle with the Yamato over planet Garmillas in June 2199, Desler evaded death.

He secretly survived and later contacted the Garmillas Provisional Government in 2203, revealing planet Garmillas faced imminent collapse within decades. This disclosure halted internal conflicts between his loyalists—including substantial AWOL elements of the Astro Fleet and Imperial Guard—and the central government. Both factions united to find a new homeworld.

Desler reorganized his breakaway fleet to cooperate with the central government on exploration. In 2205, learning of ancestral homeworld Garmann's existence, his fleet engaged the occupying Bolar Federation. Failed negotiations with the Bolar Governor-General led Desler's forces to expel the occupation and liberate Garmann.

During the Dezariam conflict, Desler's fleet stood alone against attacks after Dezariam destroyed Garmillas, as most regular Astro Fleet forces were absent. Despite Earth Federation reluctance, the Yamato's 65th Escort Corps eventually aided Desler's fleet. He then relocated his remaining forces to Galman, founding the successor state Galman-Garmillas in 2206.