R3-A3

R3-A3 was an R3-series astromech droid and member of a local rebel cell on Mykapo called the Iron Squadron. He was responsible for maintaining the Sato's Hammer systems and customized it to his own specifications. Following a skirmish with an Imperial patrol, R3-A3 and his fellow rebels came into contact with the Spectres and Phoenix Squadron. While initially reluctant to leave, R3 and his comrades Gooti Terez and Jonner Jin heeded the warnings of Ezra Bridger and Sabine Wren and managed to escape the system. However, their leader Mart Mattin was left behind. R3 took part in a combined rescue effort to save Mart. He joined forces with the astromech droid Chopper to remove a magno-mine attached to Sato's Hammer.

Background
During the Age of the Empire, R3-A3 was part of a rebel cell based on Mykapo called the Iron Squadron. He served captain Mart Mattin, Gooti Terez, and Jonner Jin and was responsible for maintaining their starship, Sato's Hammer. Mart's father was the leader of the Iron Squadron and his son succeeded him after he died. The Iron Squadron had no contact with other rebel cells including Mart's uncle Commander Jun Sato's Phoenix rebel cell. The Iron Squadron constituted the only rebel group in the Mykapo system.

Joining the rebellion
In 2 BBY, the Iron Squadron clashed with an Imperial advance patrol. Despite sustaining damage to their hyperdrive, the Iron Squadron managed to destroy their Imperial opponents with the help of the Spectres and Phoenix Squadron. Sato's Hammer destroyed a Gozanti-class cruiser by dropping several cargo containers containing explosives. Later, the Spectres docked their ship, the Ghost, with Sato's Hammer. Hera Syndulla, the leader of the Spectres and Phoenix Leader, attempted to recruit the Iron Squadron. The rebels chanced upon R3-A3 repairing the hyperdrive. R3 entered into a fight with the rebels' astromech droid Chopper, who wanted to fix the hyperdrive. Only Gooti and Ezra Bridger, one of the Spectres, managed to break up the fight. Hera's meeting was unproductive since Mart and his crew refused to leave the Mykapo system.

After Ezra convinced Hera to let him have another go at reasoning with Mart, R3 accepted help from Sabine Wren and Chopper to repair the hyperdrive. Despite repairing the hyperdrive, their efforts came to naught when Mart diverted the power to the ship's laser cannons and deflector shields. After Imperial reinforcements under Admiral Kassius Konstantine entered the system, R3-A3 along with Gooti and Jonner heeded Ezra and Sabine's warnings to leave and evacuated aboard the Phantom II, the Spectres' shuttle. However, Mart decided to stay behind and disengaged the Phantom II. He attempted to attack Konstantine's Imperial light cruiser but the ship's engines were disabled. R3-A3 and the other rebels escaped into hyperspace aboard the Phantom II.

R3-A3 later participated in a joint mission by the Spectres and Iron Squadron to rescue Mart Mattin. After the rebels learnt that Konstantine had attached a magno-mine to the hull of Sato's Hammer, Hera dispatched R3-A3 and Chopper to remove the mine. The two droids were deployed via the Spectres' starship Ghost cargo bay. R3 was afraid so Chopper pushed him into space. The two droids then activated their rocket boosters and flew to Sato's Hammer. Working together, they removed the magno-mine with R3 removing the magnetic field. The two droids then reattached the mine to cargo box hanging from Sato's Hammer. Under orders from Hera, they entered the ship's cockpit to await pick-up by the Ghost.

R3-A3 reunited with his captain aboard. Shortly later, rebel forces led by Commander Sato arrived and attacked Konstantine's Imperial forces. After the Ghost picked up Sato's Hammer, they dropped the bomb-laded cargo box onto Konstantine's ship. The resulting explosion badly damaged the cruiser and allowed the rebels to flee just as Grand Admiral Thrawn entered the system in the Chimaera. Later, R3 reunited with the other rebels at Chopper Base on the planet Atollon. He witnessed Mart hugging his uncle Jun, Jonner, and Gooti.

Personality and traits
R3-A3 was a temperamental and territorial astromech droid who maintained the systems aboard the Sato's Hammer. While he was initially bristling at help from Chopper, the two came to form a strong bond and joined forces to repair the ship's hyperdrive and to remove a magno-mine. R3 had a conical head, like those of the R4 astromech line, and was equipped with a rocket booster.

Behind the scenes
R3-A3 and the rest of Iron Squadron first premiered on the eponymous Disney XD Star Wars Rebels episode "Iron Squadron", which premiered on November 11, 2016.