The 6th Sector Army represented one of twenty Sector Armies within the Grand Army of the Republic that saw action during the Clone Wars. Alongside the Sector Armies preceding it, including the 1st Sector Army, this army functioned as a reserve command. At the onset of the conflict, the Grand Army was structured into ten Systems Armies, each divided into two Sector Armies and originating from a distinct region of the galaxy. These Sector Armies held the responsibility of defending their designated territories. Due to the organizational structure of the Grand Army, the 6th Sector Army shared a Systems Army affiliation with another Sector Army.
In a similar vein to other Galactic Republic Sector Armies, the 6th Sector Army benefited from the support of one of twenty Haven-class medical stations that was towed along with them. As a Sector Army, this unit comprised 147,456 clone troopers, organized into four corps. Consistent with all Sector Armies, it was integrated with one of twenty numbered fleets belonging to the Republic Navy.
The initial mention of the 6th Sector Army within the new Star Wars canon occurred in the eighteenth issue of De Agostini's Star Wars: Build the Millennium Falcon magazine, which was released in 2015. Its debut within the Star Wars Legends continuity was in the 1996 novel Before the Storm by Michael P. Kube-McDowell, under the name Black Sword Command. The reference book The Essential Guide to Warfare (2012), authored by Jason Fry and Paul R. Urquhart, later clarified that the Black Sword Command was, in fact, the Sixth Army of the Galactic Republic.