First of all, to debunk the popular Trotskyist origins of Neo-Conservatism narrative, watch these videos from InDefenseOfTooucan, I’m not a Trotskyist but they are a Trotskyist YouTuber I respect.
What most people typically mean when they refer to someone as a “Neo-Con” is the most Hawkish Pro Intervention people in the Republican Party in contrast to Non Interventionist Paleo-Cons. Specifically how such Foreign Policy aims were framed during the Cold War and War on Terror. Anyone meaning anything more specific than that is frankly referring to something that doesn’t even really exist., rarely has anyone actually called themselves a Neo-Con.
The core of Neo-Con ideology was defined by the magazine National Review and its founder William F. Buckley Jr. Buckley was a Yale Graduate who is known to have worked for the CIA for two years at the start of the 50s including one of those for E. Howard Hunt in Mexico City.
When he launched National Review in 1955 he made a point to hire intellectuals who were Ex-Communists of some sort. This is tied to the basis for the Trotskyist claim, but the small number of Trotskyists among them were specifically Shachmanites, a sub group disowned by both Trotsky himself and James P. Cannon and are people who ultimately fell out even with Shachman. What most of them do happen to have in common is having all worked for either OSS or CIA at some point previously as they transitioned into abandoning The Left. James Burnham is perhaps most important as the Magazine's lead writer on Foreign Policy specifically. Whitaker Chambers proved a valuable spy because he’d spied for the Soviet Union when he was a Communist, a rare example of that McCarthyist accusation being true (usually Soviet Spies did not publicly claim to be Communists or participate in the CPUSA).
But going outside the realm of intellectuals. Allen Dulles and his brother John Foster Dulles were major players in the internal politics of The Republican Party and were in fact key players in the early rise in political importance of both Prescott Bush and Richard Nixon.
Irving Kristol was part of the Congress for Cultural Freedom, a known CIA operation. However I don’t consider Irving Kristol important actually, he and many others you usually see named as the key Neo-Conservatives are part of the Genre of historical figures whose importance as “behind the scenes” political players is grossly exaggerated while just so happening to be Jews. However since Kristol is the only person who has ever really self identified as a Neo-Con I couldn’t ignore him completely.
