Saw Gerrera was a loyal follower of King Ramsis Dendup, the benevolent monarch of Onderon who attempted to keep his world apart from the tensions of the Clone Wars. Saw believed firmly in independence, and did not want to see his planet thrust into galactic warfare. But Dendup was ousted by King Sanjay Rash, who committed the world to the Separatist cause. Saw was one of the fervent young loyalists who refused to acknowledge Rash's rule, and openly rebelled against the crown. He and his sister Steela were cast out of the walled city of Iziz and forced to live in ruins amid the jungles of Onderon, but formed a rebellion.
While he learned the art of combat from Jedi, Saw Gerrera became a rebel leader in his own right. After the Clone Wars, he continued the fight against the Empire, garnering a reputation as an effective soldier -- but over time he became more extreme in his methods. This was evident in one particular mission on Geonosis.
Saw and his team went to the barren planet after the Ghost crew had reported the entire population was gone. There was one survivor, however, and this Geonosian methodically took out Saw's team. Gerrera was determined to find this "bug" and make him talk -- through any means necessary -- about what the Empire had been building on Geonosis.
The Ghost crew soon arrived, sent by the Alliance to recover Saw and his crew. But Saw ended up saving the small team from the Geonosian’s battle droids. Together, they found the sole Geonosian, and discovered that he was the last of his kind; the Empire had indeed wiped out the Geonosians. But the alien, who the rebel Ezra nicknamed Klik-Klak, was protecting a queen egg -- the key to his people’s survival. That’s why he destroyed Saw’s team. Still, that mattered little to Gerrera, who didn’t trust Klik-Klak. Moreover, Gerrera believed the Ghost crew was too soft, and wanted to question Klik-Klak his way, off-planet. But when the Empire arrived, they put aside their differences.
Klik-Klak eventually took the rebels to the deep underground of Geonosis, where they found two empty canisters emblazoned with the Imperial cog. The canisters had carried poison gas, and were the weapons used to eliminate the Geonosians; as such, they could prove the Empire had committed atrocities. When the rebels had to make a quick escape, however, they lost the canisters in the process. In the end, Saw agreed that Klik-Klak should stay on Geonosis, showing that years of war had made him extreme, but did not destroy his humanity. Though, he was still fearful that they were too late in discovering what the Empire was up to on the planet…
Gerrera encountered the Ghost crew once again -- after the Rebellion ignored his warnings about an Imperial relay. He rescued Sabine, Ezra, and Chopper from a failed mission, destroying the relay in the process. Later, he used the rebels to infiltrate a freighter holding secret Imperial cargo: a massive kyber crystal. Determined to stop the Empire from using the crystal, he drove Ezra's lightsaber into its core. The crystal became unstable, exploding and taking a Star Destroyer with it, while Saw and the rebels made their escape.