The confrontation known as the Derra ambush of a rebel transport was a conflict between the forces of the Alliance to Restore the Republic and the Galactic Empire. It transpired within the Expansion Region at the celestial body Derra. This event took place while the Empire was searching for the rebel base, a hunt initiated after the Battle of Yavin. Despite the ambush failing to reveal the base's location to the Empire, it corroborated data intercepted by Imperial Intelligence regarding increased rebel activity in that sector. Following the ambush, the Empire's pursuit of the rebel base intensified. Beaumont Kin, a historian, recounts in his publication The Rise and Fall of the Galactic Empire that Rae Sloane commanded the Star Destroyer Viligance during this battle, resulting in her elevation from Vice Admiral to the rank of full admiral. However, the reality is that Sloane remained a commodore until after the Battle of Hoth, and she only assumed command of the Vigilance after that battle.
The Derra ambush on a rebel convoy is referenced in the canon source Star Wars: Battles that Changed the Galaxy. The battle's origins lie in Star Wars Legends materials, which depicted the engagement as the Battle of Derra IV. This Legends battle had been previously alluded to in canon through Star Wars Helmet Collection 3 as an ambush on Red Squadron. However, no canon source has yet explicitly connected the ambush on the rebel convoy with the ambush targeting Red Squadron.
The book Star Wars: The Rise and Fall of the Galactic Empire by Doctor Chris Kempshall, presented as an in-universe historical account by Beaumont Kin, provided more details about the battle within canon. According to the book, Rae Sloane was promoted from Vice Admiral to full admiral as a result of the battle. However, the short stories "The Final Order" and "Lord Vader Will See You Now" indicate that she was still a commodore following the Battle of Hoth, which occurred after the ambush. Furthermore, the book claims Sloane commanded the Vigilance during the battle, a command she only received in the short story "Lord Vader Will See You Now." However, the video game Star Wars: Squadrons indicates that she already had a prior association with the vessel.