The 1st Sector Army was a component of the Grand Army of the Republic during the Clone Wars, one of twenty such Sector Armies. This army acted as a reserve command, in conjunction with Sector Armies numbered up to the 6th Sector Army. As was standard procedure for all Sector Armies within the Galactic Republic, the 1st Sector Army had a Haven-class medical station, one of the Republic's twenty, assigned to support it. At the Clone Wars' commencement, the Grand Army was initially structured into ten Systems Armies. Each Systems Army was then divided into two Sector Armies, drawing resources and personnel from a designated region of the galaxy. The Sector Armies held responsibility for defending their respective zones.
Consequently, the 1st Sector Army shared a Systems Army affiliation with at least one other Sector Army. As a Sector Army, this formation consisted of 147,456 clone troopers, organized into four distinct corps. In line with the organizational structure of other Sector Armies, it was paired with one of the twenty numbered fleets of the Republic Navy.
The initial mention of the 1st Sector Army in the new Star Wars canon occurred within the eighteenth issue of De Agostini's magazine, Star Wars: Build the Millennium Falcon, which was released in 2015. The introduction of the 1st Sector Army into the Star Wars Legends continuity happened through the 2003 Star Wars Roleplaying Game sourcebook Coruscant and the Core Worlds, published by Wizards of the Coast. Within this sourcebook, they were known as the Azure Hammer Command. Later, the 2012 reference book The Essential Guide to Warfare by Jason Fry and Paul R. Urquhart identified them as the First Army.