Sector 21505

Sector 21505 is a strategically-important area of space to both the Federation and the Cardassian Union and was often the location of several skirmishes between the two beginning in the 2340s. The Demilitarized Zone slices along a portion of the sector's boundaries. Parts of it were also hotly contested both during the Klingon-Cardassian War of 2373 and the Dominion War. The sector offers some of the best travel and trade routes between the Cardassian Union and major Federation worlds such as Betazed, Risa, and later Bajor. These same routes were utilized by the Dominion, making them important areas to defend for the Federation Alliance.

Eighty-nine percent of the sector lies in Cardassian space and contains over a dozen inhabited worlds, such as Volon III (Volon System) and Trelka V (Trelka System). It also is home to the Cuellar System that borders Federation space, which the Cardassians (and later Dominion) used to launch offensive operations. In 2367, Capt. Benjamin Maxwell took his ship the USS Phoenix into this system and attacked several military installations and transports, believing the Cardassians were building up for an invasion. (TNG: "The Wounded")

Following the Federation-Cardassian Treaty of 2370, several worlds in this sector changed hands. The colonists on Salva II, angry at having to give up their planet to the Cardassians, refused Federation relocation and settled on the Maquis-controlled world of Marva IV. (DS9: "For the Uniform")

Starbase 310 is located in the Alpha Trianguli System on the Federation side of Sector 21505. Roughly half of the Argolis Cluster also falls within its boundaries.