Retsub was an EF76 Nebulon-B escort frigate in the Imperial Navy during the Galactic Civil War. Towards the end of Operation Skyhook the Empire began a new offensive after the completion of the Death Star I. The Retsub was assigned to one of the first attacks, against one of the Alliance to Restore the Republic's main weapons-storage compounds. The Alliance had, however, already gotten word of the increased Imperial activity and taken steps to protect the cache, sending three R-22 Spearheads from Red Squadron, led by Keyan Farlander, to defend it until relieved by Blue Squadron's R-22s.