G-8 was a heroic First World War flying ace and spy whose exploits were chronicled in pulp novels by Robert J. Hogan in the 1930s and 1940s. His true name was never revealed. His adventures were wild and bizarre when compared to some of his contemporaries, as he battled not just the normal German flying aces and spies, but also such monstrosities as giant bats.
Philip José Farmer on G-8
In Tarzan Alive, Philip José Farmer proposed that, following the war, G-8 returned to the United States and developed a split personality, with each of the personalities setting up as separate vigilantes - i.e, two other celebrated pulp characters, Lamont Crantson/Kent Allard (aka The Shadow) and Richard Wentworth (aka The Spider).
Farmer later distanced himself from this theory in the pages of Doc Savage: His Apocalyptic Life, having successfully identified G-8 as one Bruce Hagin Rassendyll, one of two sons of Ralph Rassendyll and Rhoda Delagardie. The other brother was Allard Kent Rassendyll, and Richard Wentworth was listed as an elder half-brother on their mother's side.
Farmer also utterly disproved his original theory with the publication of the Watson manuscript The Adventure of the Peerless Peer (also published, in a revised edition, as "The Adventure of the Three Madmen") - although in this book G-8 is portrayed as a delusional aviator named Wentworth.
G-8 and Captain Midnight
In his 1974 article "The Life Story of King Kong", Jim Harmon identified G-8 and his Battle Aces not only with the pilots who shoot down the giant ape of that name, but with another heroic aviator of both World Wars, James Albright, known to his contemporaries as "Jim" or "Red", and to radio listeners in the 1930s and 1940s as Captain Midnight. Presumably Harmon was aware of Farmer's work on the Rassendyll family,who are of course notorious for producing red-headed throwbacks every generation or so.