Saw Gerrera was a human male Onderonian resistance fighter who, as a leading member of the Onderon rebels, fought against the Confederacy of Independent Systems on Onderonduring the Clone Wars. He and his sister, Steela Gerrera, were instrumental in the rebel liberation of their homeworld during the Onderonian Civil War. He later became a key member in the fight against the Galactic Empire and the formation of the Alliance to Restore the Republic. His tactics against the Empire led him to be seen as an extremist, one whose notoriety was recognized by the Empire and, many years later, the New Republic.
In the early resistance against the Separatist Alliance on Onderon, Gerrera and his fellow soldiers were outnumbered and out-fought by the Separatist Droid Army. They requested help from the Jedi High Council, which led the Grand Army of the Republic in its fight against the Separatists, but the Jedi Order chose not to become actively involved in the fighting on Onderon. Instead, they sent a team of advisors—GeneralsAnakin Skywalker and Obi-Wan Kenobi, Commander Ahsoka Tano, and Clone Captain CT-7567 ("Rex")—to train the Onderonian fighters. The Jedi and Captain Rex taught them proper techniques and strategies for taking on the battle droidarmy, and, through their efforts, the rebels began to turn the tide. Gerrera came to resent that the rebels chose Steela as their leader, and he was soon captured in an ill-concocted solo effort to rescue the deposed King Ramsis Dendup from the Separatists. They were both rescued by the rebels, who eventually mounted a final battle against the Separatists. Through their efforts, the rebels liberated their world and returned Dendup to the throne. The fight, however, came at a personal cost: Steela was killed during the final battle, and Gerrera was left to mourn his sister—feeling responsible for her death.
At the end of the Clone Wars, the Republic was transformed into the Galactic Empire. Later, Saw brought Galen Erso, Lyra Erso, and Jyn Erso to the uninhabited planet of Lah'mu. When Orson Krennic took Jyn's parents away from her, Saw found her and raised her until she was a young adult. Gerrera fought against the Imperial Military and led a resistance group known as the Partisans, a militant organization that some considered an extremist organization with terrorism tactics. His resistance cell, a continuation of his Onderonian resistance, was one of the first in the group of cells that formed the Rebel Alliance. He was later involved in the early campaigns of the Rebel Alliance, by which time his more-extreme tactics had come to stand in stark contrast with those of Alliance leaders Bail Organa and Mon Mothma. He eventually based his group on Jedha, where he began to engage in questionable fighting method.
(Source Star Wars wiki)