In the era of 0 BBY, specifically a few days preceding the monumental Battle of Yavin, the Alliance to Restore the Republic successfully seized the Imperial BFF-1 bulk freighter known as Sidral II.
Upon discovering the Empire's secret construction of the Death Star, a battle station with the capacity to obliterate an entire planet, the Alliance embarked on a mission to identify the various contractors involved in its creation.
As an element of this strategic undertaking, Tuz, a Mon Calamari privateer, played a crucial role in the capture of the Sidral II. At the time of its capture, the freighter was transporting a shipment of military supplies, including timers and fusion shells. Subsequently, the Alliance dispatched the CR90 corvette named Frazier to meet with the freighter and transfer its valuable cargo. The Imperial-class Star Destroyer Immortal disrupted this operation. However, the Rebel forces managed to complete the transfer before successfully jumping to hyperspace.
A portion of the acquired shipment had previously been processed through an Imperial repair facility situated near Coruscant, the capital of the Empire. Consequently, Alliance High Command made the decision to initiate an attack against the repair dock, with the objective of disrupting the infrastructure supporting ships involved in the Death Star project.
Although X-Wing Collector's CD-ROM: The Official Strategy Guide initially indicated that Operation Skyhook commenced following the capture of the Tantive IV, later sources, including The Essential Atlas, clarified that this sequence is logically flawed. This is because the second phase of Operation Skyhook involves obtaining the Death Star plans, which are subsequently transmitted to the Tantive IV.