Z-Fighters

Z Fighters (Ｚ戦士, Zetto Senshi; also known as the Z Warriors or Earth's Special Forces, or even the Gold Fighters by Mr. Satan) are a small group of warriors located on Earth. Their duty is to defend Earth from major threats and to protect the seven mystical Dragon Balls from the hands of evil. Goku is the 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.

Origins
A similar team already existed in the Dragon Ball anime, 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.

Formation
The battle 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 and his Saibamen, 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 Battle on Planet 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.

Android conflict
It was not until the Android conflict some four years after the conflict on Namek that the team of the Z Fighters came full circle. Goku returns from space one year after defeating Frieza, while Future Trunks comes from the future to warn everyone about the Androids that have caused apocalyptic mayhem in his time. After his defeat on Earth and then brief alliance on Namek, Vegeta decides to return and remain on Earth in anticipation for Goku's return in the hopes that he would be ready to challenge his rival once again. When Future Trunks reveals the future, Vegeta decides to stay and train for the upcoming conflict with the androids rather than prepare to battle Goku, though like previously with Piccolo, most of the other Z Fighters do not fully trust him and are unwilling to consider him a true ally. Krillin, Yamcha, Tien Shinhan, and Chiaotzu, who were wished back to life, also begin training for the fight with the androids. It is evidently around this time that the series refers to the group of warriors as the "Z Fighters". When the androids do arrive, Future Trunks returns as well, bolstering the team's ranks. With Goku, Gohan, Piccolo, Krillin, Yamcha, Tien Shinhan, Chiaotzu, Vegeta, and Future Trunks, the group fully forms and it is shown through the opening sequence at this time in the series (the final image is of the aforementioned fighters and Goku as he transforms into a Super Saiyan).

It is also worth noting that while this version of the Z Fighters is a prominent one during the series history, it is the only period of time in which the team consists of these certain members, the largest roster of the Z Fighters. By the end of the Cell Games, Goku is dead and Gohan has become Earth's primary defender. Future Trunks returns to his timeline more powerful than ever, thanks to his training in the Hyperbolic Time Chamber with Vegeta, and proceeds to finally destroy the evil versions of Androids 17 and 18 in his world, as well as his timeline's Cell a while later.

Meanwhile, Tien Shinhan bids farewell to the Z Fighters and plans to live in seclusion with his best friend Chiaotzu, realizing he can no longer compete with the powers of the Super Saiyans. Yamcha retires from fighting for the same reasons as Tien. Krillin continues to live with Master Roshi, and after a few years, eventually reunites with and later marries Android 18. They soon have a daughter named Marron, and thus Krillin stops training as well. Piccolo decides to live with Dende and Mr. Popo on Kami's Lookout, continuing to train and meditate there. Vegeta continues to train hard too, hoping to become a Super Saiyan 2 like Gohan, but declares that he will never fight again with his only rival, Goku, dead. Finally, Gohan keeps his promise to his mother Chi-Chi and gives up fighting to study and become a scholar.