Short answers, pulled from the story.
The manga series Tetsujin 28-go was created by Mitsuteru Yokoyama after he returned from evacuation to find his hometown of Kobe flattened by B-29 bombers. The story centers on a giant robot designed as a secret weapon for the Imperial Japanese Army during the final phase of the Pacific War.
The 1963 television series Tetsujin 28-go was the first humanoid giant robot to be controlled externally via a remote control by an operator. The protagonist Shotaro Kaneda stood on the ground and manipulated a control box to dictate every movement of the steel giant instead of piloting it from within a cockpit.
Fred Ladd renamed the series Gigantor because the Marvel Comics character Iron Man had already claimed the name Iron Man in the United States. The adaptation stripped away the wartime setting and pushed the year forward to 2000 to fit the American market of the early 1960s.
The main antagonist in the original 1960s series Tetsujin 28-go is Dr. Black Dog, a reclusive mad scientist who built dangerous robots for criminal purposes. His creation the Black Ox served as a dark mirror to Tetsujin 28-go and represented the duality of technology and the potential for destruction.
The 2004 television series Tetsujin 28-go returned to the roots of the original manga by setting the story ten years after World War II and restoring the historical context. This version was released in the United States under its original name Tetsujin-28, marking the first time a property had not been localized to Gigantor in English-speaking nations.
Guillermo del Toro cited the series Tetsujin 28-go as a major influence on his movie Pacific Rim, which depicts battles between human-controlled giant robots and giant alien monsters. The legacy of the series also permeated the works of Katsuhiro Otomo, who borrowed Shotaro's name for the protagonist of his manga Akira.