The New Z Fighters are a group of strong characters that come together to put an end to evil in Dragon Ball SS. It is a recreation of the Z Fighters. Their duty is to defend Earth from major threats and to protect the seven mystical Dragon Balls from the hands of evil. Goku was the original de facto leader of the group due to his incredible success rates against villains in Dragon Ball, victory over the Saiyans, and his victory over Frieza. Over time, the group consistently bolstered its ranks through the addition of former enemies and new heroes and routinely overcame seemingly insurmountable opponents, always emerging victorious against progressively more powerful foes.
Main article: Z Fighters
During the Dragon Ball anime, a similar team existed, but it was called the Dragon Ball Gang. Their original purpose for coming together was not to protect the Dragon Balls, but to use them themselves. Typically, this brought the group into conflict with a host of villainous characters who sought to use the Dragon Balls for power, whereas the Dragon Ball Gang desired the balls for good. This included evils such as Emperor Pilaf and the Red Ribbon Army. The team that could be considered an early rendition of the Z Fighters was formed mainly in response to the threat posed by King Piccolo and later his son in the ultimate story arc of Dragon Ball. Its members consisted of Goku, Krillin, Yamcha, Tien Shinhan, Chiaotzu, Yajirobe and their supporters.
The first actual formation of the Z Fighters was out of necessity, brought on when Goku was faced with Raditz, who had kidnapped his young son Gohan and wanted to destroy the Earth. Goku formed an alliance with his arch rival Piccolo in order to fight for a common cause. The team-up is considered the true birth of the Z Fighters.
The term itself is very rarely used in the series by anyone other than the narrator. The first being in the Androids Saga, when Future Trunks explains to Goku that in the future, "the Earth's Special Forces are gone." The Second character to use the term was Gohan when he was training in the Hyperbolic Time Chamber to defeat Cell. While sleeping, he had a dream in which his mother Chi-Chi said she did not want Gohan to be in Goku's little gang. Gohan then responds that he is not in a little gang, he is a Z Fighter.
The battles against the Saiyans, Vegeta and Nappa, is commonly considered the first time Earth's Special Forces engaged enemies together. After Goku's death against Raditz, Piccolo trained Gohan to prepare for the arrival of the saiyan warriors Vegeta and Nappa. Though several of the members expressed distrust of their former enemy Piccolo, this first Z Fighter roster consisted of Goku, his inexperienced son Gohan, Piccolo, Tien Shinhan, Krillin, Yamcha, and Chiaotzu. Yajirobe, though choosing not to join the fight, ended up playing an important role in repelling Vegeta by slicing off the Saiyan's tail, saving Goku's life. Unfortunately, the Z Fighters were decimated in the battle against Nappa, with only Goku, Krillin, Gohan, and Yajirobe surviving the fight. The deceased would train in Other World with King Kai like Goku, while the survivors (sans Yajirobe) headed to Namek to use their Dragon Balls.
During the conflict on Namek, Earth's Special Forces would ally with the Namekian race against Frieza and his Planet Trade Organization, this part of the series marked a turning point for the group, as Piccolo fully reformed and they began working with Vegeta, if not out of necessity in the fight against Frieza. This is also the first time in the series in which a character actually refers to the group as the Z Fighters, when Gohan pleads with Chi Chi to be allowed to go to Namek with Krillin and Bulma. He informs her that he too is a Z Fighter, and must be there to protect his friends.
Main article: List of New Z Fighters members