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 were cast out of the walled city of Iziz and forced to live in ruins amid the jungles of Onderon. There, Saw plotted against Rash's draconian rule, and with trepidation accepted off-world support from the Republic.
The Onderonian rebels had a very loose command structure, and Saw filled the need for leadership with his passionate drive to restore independence to Onderonians and rid the planet of off-world interests. Saw's fiery determination often made him short-tempered, much to the chagrin of fellow rebels Steela Gerrera and Lux Bonteri.
Onderon is an ancient planet where civilization has held back the jungle wilds with fortified wilds protecting its massive cities.
Saw's sister Steela is a crack shot with her sniper rifle and a capable warrior. She is not as outspoken as her unrestrained brother.
Saw looks down his nose at Lux Bonteri, the planet's nominal Senatorial representative. Saw believes words and politics have done Onderon little favor, and questions Lux's effectiveness in the rebellion.
Anakin saw an opportunity in the fierce dedication exhibited by the Onderon rebels. He proposed a controversial idea to the Jedi Council -- secretly arm the insurgents to wage war against the Separatists.
Ahsoka Tano was assigned to covertly arm and train the rebels. Saw was impressed with what he saw in the Padawan -- in her combat skills and perhaps more.