The Shield was introduced in Pep Comics #1 in 1940, while his counterpart was introduced in 1965 yet existing fictionally in the 1940's. One was G-Man Joe Higgins, an aspiring scientist seeking to avenge the death of his father and discovering a process that gave him super-strength and an invulnerable costume. The other was G.I Rip Jagger, an aspiring ninja seeking to avenge his comrades whom he saw die and discovering a secret society of ninjas on a Pacific Island, gaining super-human skills and a special costume. While looking like walking posters for America and Japan, their costumes gained their color scheme due to a special chemical process (in the Shield's case) and the style-sense of the ninja society (in the Judomaster's case). Both picked up kids sidekicks, Dusty and Tiger.
Due to sabotage on the part of an adversary, Shield lost his powers for the duration of the war yet continued to fight against evil agents from overseas, while Judomaster himself had to struggle to overcome a handicap of his own imposed on him by a foe, blindness. Both persisted in their heroic careers, thanks to proddings from the boys' own courage.
They faced rogues galleries which challenged their physical dexterity. The Hun, the Strangler and the Fang plagued Shield; while the Smiling Skull, the Acrobat, and Mountain Storm. None matched the heroes in battle!
Each also had other assisting them. For Judomaster, it was Sensei, Bushiri, and his beloved Suzikawa. For the Shield, it was the Wizard, Steel Sterling, Hangman, Black Hood, Captain Flag, Sgt Boyle and Shield's wife Ellie.