Attack on Phoenix Squadron ( 3 BBY ) An attack on the rebel cell Phoenix Cell fleet was launched by Admiral Kassius Konstantine . The fleet was waiting for fuel to be delivered by the crew of the " Ghost " before it could jump into hyperspace en route to the Yost system , where the rebels intended to set up a base . They soon learned , however , that the Yost system was under Imperial control and the rebels would be jumping into a trap . With the help of an Imperial inventory droid named AP - 5 , the rebel astromech droid Chopper was able to discover a new location : Atollon . The rebels jumped away from the attack and arrived safely in Atollon . Prelude . Following the theft of the Imperial fighter carrier above the planet Ryloth , the Phoenix Cell continued their search for a permanent rebel base . By cross - referencing several Old Republic and Lasat star maps , the rebels had decided to settle on Berzite ' s moon in the Yost system at the urging of Ketsu Onyo ; Sabine Wren ' s friend . However , the rebel fighter carrier lacked sufficient fuel to travel to the Yost system . Consequently , the Spectres were dispatched on a mission to steal fuel from the Imperial depot at Horizon Base . The rebels managed to steal the fuel but the astromech droid Chopper was left stranded after he was distracted by a new droid leg . Despite being pursued by Imperial stormtrooper s , Chopper managed to stow aboard an Imperial cargo ship called Cargo transport 241 . There , he struck an unlikely friendship with an Imperial inventory droid named AP - 5 , who had been a veteran of the Clone Wars . Working together , the two droids knocked out the ship ' s captain and seized control of the vessel . They also jettisoned the ship ' s cargo compartment and the stormtrooper garrison in space . The battle . As soon as the Spectres returned to the rebel fleet , they discovered that it was under attack by an Imperial fleet . Recognizing the rebel starship " Ghost " as the same vessel that had raided the Imperial depot at Horizon Base , Admiral Kassius Konstantine realized that the " Ghost " was carrying fuel for the rebels and ordered his ships to focus their fire on the " Ghost " . The " Ghost " was pursued by several TIE fighters but Ketsu came to the rebels ' aid in her starship " Shadow Caster " . After breaking through the Imperial ships , the " Ghost " managed to land inside the rebel fighter carrier . While Ezra Bridger and Garazeb Orrelios were unloading fuel , Chopper managed to contact the " Ghost " and informed Captain Hera Syndulla that he had managed to steal an Imperial cargo ship . When Hera mentioned that the rebel fleet was preparing to depart for the Yost system , AP - 5 quickly warned the rebel captain that an Imperial fleet was lying in ambush there . After Chopper vouched for AP - 5 , Hera agreed to trust the former Imperial inventory droid . After cross - referencing both Chopper and Imperial data , AP - 5 identified the planet Atollon as a safe haven with no Imperial presence . Using AP - 5 ' s information , Hera warned Commander Jun Sato and the other rebels that the Yost system was unsafe . Before AP - 5 could transmit the new hyperspace coordinates for Atollon , he and Chopper were accosted by the Imperial ship captain , who had woken up . Following a struggle , Chopper managed to subdue the Imperial but not before the captain shot AP - 5 twice with his blaster ; severely damaging the droid . Chopper then completed AP - 5 ' s work by transmitting the rest of the coordinates to Hera , who in turn relayed them to Commander Sato . Due to AP - 5 ' s information , the Phoenix rebels were able to escape the Imperial trap and reached Atollon . Aftermath . After the rebel fleet reached Atollon , they were rejoined by Chopper and AP - 5 . After Sabine repaired AP - 5 , the inventory droid decided to join the rebellion at the advice of Chopper . While the rebel fleet remained in orbit , rebel forces under the former Clone Captain Rex began building a base on Atollon . In honor of Chopper , the new base was named " Chopper Base " . Rebel efforts to establish the base encountered a major obstacle in the form of several predatory spider - like creatures known as krykna . The krykna devoured Lieutenant Dicer and kidnapped Rex , who was subsequently rescued by the Spectres . Unwilling to abandon the base , the rebels constructed a perimeter fence consisting of sensor markers ; a security technology that irritated the krykna and kept them away . Behind the scenes . The attack on the rebel fleet served as the climax of the " Star Wars Rebels " episode " The Forgotten Droid " , which first premiered on Disney XD on March 16 , 2016 . It introduced several new characters and plot elements including the inventory droid AP - 5 ( who was voiced by Stephen Stanton ) , the Unidentified Imperial cargo ship captain ( James Adomian ) , and the planet Atollon .