Guardian Squadron was one of the three Y-wing squadrons that made up Defender Wing. The other two were Champion and Warden Squadrons.
Guardian Squadron was under the personal command of General Horton Salm. The Squadron took part in the failed attack on Borleias six and a half years after the Battle of Yavin. Defender Wing was instrumental in saving Rogue Squadron from certain destruction during the assault.
Defender Wing fought in the Yag'Dhul system, again with Rogue Squadron, in order to capture a supply of bacta during the Bacta War.
At some point during the Galactic Civil War, Guardian Squadron was equipped with BTL-S8 K-wing assault starfighters.
During the Thrawn Crisis, Guardian was reequipped with B-wings and subsequently took part in the New Republic's campaign against the rogue Imperial Admiral Delak Krennel.