When animator Bruce Timm took on the challenge of adapting the Justice League comic book and turning it into an animated sequel, the line-up of this new JLA adaptation was created with two things in mind: to pay tribute to the original line-up of the Justice League of America while also reflecting racial and cultural diversity.
John Stewart, an African-American Green Lantern who had previously worked with the League in the comics, was chosen rather than one of the better-known modern-era Green Lanterns (Hal Jordan, Guy Gardner or Kyle Rayner). In addition to his race, the producer felt Stewart's original abrasive personality would have more dramatic potential.
In the DC Animated Universe, John Stewart was recruited by the Green Lantern Corps and trained for ten years, before returning shortly after Abin Sur's death. He became a founding member of the Justice League.
John Stewart possessed no innate superhuman abilities, apart perhaps from a nearly-indomitable will. He was also unfailingly honest and virtually without fear. These qualities made him an ideal candidate for membership in the Green Lantern Corps.
John's military experience provided him with a strong grasp of tactics, and made him a formidable combatant — armed or unarmed. On two separate missions he went into battle without his ring, and fared well.
Like all members of the Green Lantern Corps, John Stewart was issued a Power Ring and a lantern-shaped Power Battery.
Thus equipped, John was extraordinarily well-prepared for the mission of maintaining order within his assigned space sector.