During Operation Skyhook, the Empire made a surprise attack on the command ship Defiance near Bestine IV, site of an important Rebel base. The Imperial-class Star Destroyer Immortal just ended its hyperdrive jump next to the Mon Calamari Star Cruiser Defiance.
The Star Destroyer Immortal entered the system and deployed its TIEs. Red Squadron's X-wings and Blue Squadron's A-wings managed to destroy many Imperial starfighters and allowed the Defiance to escape in hyperspace.
- X-Wing: The Official Strategy Guide
- The Complete Star Wars Encyclopedia