Comic publishers have always dutifully scanned popular culture for clues as to topics that appear to interest teenagers. In the 1950s, comics were produced to capitalize on the appeal of Westerns at the movie theatre. When monster movies were popular, monster comics were not behind. And when spies and secret agents became hip in the mid-1960s, the publishers rushed to fill the demand.
Marvel made a particulary strong entry into the secret agent genre with the paranoia-tinged Nick Fury, Agent of Shield series. NFAS took over the lead feature in Strange Tales that had previously belonged to the Human Torch (and briefly, Torch and the Thing team-ups) effective with issue #135, featuring a terrific cover by Jack Kirby:
(Note: Fred Hembeck has a cool takeoff on this cover and some memories of the NFAS Saga in the January 17, 2006 edition of his blog.)
Fury had been a character in the Marvel universe for several years already, albeit as a historical character. He was Sgt. Fury, leader of the Howling Commandos, a World War II fighting squadron. Now Marvel decided to age him a few years (but not quite the 20 that the calendar called for) and make him a secret agent.
S.H.I.E.L.D. of course was a direct swipe of U.N.C.L.E. (which was probably a swipe itself of S.P.E.C.T.R.E.) and stood for Supreme Headquarters International Espionage Law-Enforcement Division. Shield's chief enemy was a group called Hydra, which mercifully does not stand for anything, but does have some cool rituals:
NFAS was blessed with great stories and artwork. After handling the introductory story in Strange Tales #135, Jack Kirby did layouts for the amazing Johnny Severin for the next few issues, followed by a year or so of rotating artists including Ogden Whitney (!). Finally in Strange Tales #151, a new artist was hired for the feature who would define Agent of Shield for the next few years: Jim Steranko. Steranko's style was unlike most comics artists of the time; he was heavily influenced by the psychedelic posters and album art of the late 1960s as this cover shows:
In early 1968, Marvel decided to quit doing anthology magazines. Strange Tales was changed to Dr Strange with issue #169, and Nick Fury Agent of Shield was given its own title starting with #1. Unfortunately the title struggled a bit on its own apparently, possibly because of the inevitable decline of the secret agent genre after the initial fad died down. The first twelve issues of NFAS were published on a monthly basis, but with #13, the frequency was changed to bi-monthly and the title only lasted to #15. A year later Marvel published three more issues but they were reprints of the early Strange Tales stories.