The Devil's Chessboard by Dave Talbot,he starts with the Dulles brothers..

[...Foster still could not bring himself to cut off his former Berlin law partner, Gerhardt Westrick, when he showed up in New York in August 1940 to lobby on behalf of the Third Reich. Setting himself up in an opulent Westchester County estate, Westrick invited influential New York society types for weekend parties, taking the opportunity to subject them to his pro-Hitler charm offensive. Westrick’s guest lists were dominated by oil executives because he was particularly keen on ensuring the continued flow of fuel supplies to Germany, despite the British embargo. The lobbyist finally went too far—even by the hospitable standards of the New York society set—when he had the gall to throw a gala party at the Waldorf-Astoria on June 26, 1940, to celebrate the Nazi defeat of France. Westrick’s shameless audacity created an uproar in the New York press, but Foster rushed to the Nazi promoter’s defense, insisting he had “a high regard for his integrity.”

Until late in the day, Foster harbored sympathy for the devil himself, Adolf Hitler. Even after the Nazi regime pushed through the anti-Semitic Nuremberg Laws of 1935 and unleashed waves of terror against Germany’s Jewish population, Foster clung to a sympathetic view of the Führer. He could not help being impressed by a man “who from humble beginnings . . . has attained the unquestioned leadership of a great nation,” Foster told a friend in 1937. By 1939, Eustace Seligman—a Jewish senior partner at Sullivan and Cromwell—had become so fed up with Foster’s position on Nazi Germany that he confronted his boss, telling Foster he was hurting the firm’s reputation by publicly suggesting “that Germany’s position is morally superior to that of the Allies.”

Like his brother, Allen Dulles was slow to grasp the malevolence of Hitler’s regime. Dulles met face-to-face with Hitler in the Führer’s Berlin office in March 1933. He was ostensibly on a fact-finding mission to Europe for President Roosevelt, but Dulles was particularly interested in determining what Hitler’s rise meant for his law firm’s corporate clients in Germany and the United States. As Dulles subsequently informed Foster, he did not find Hitler particularly alarming. And he was “rather impressed” with Joseph Goebbels, remarking on the Nazi propaganda chief’s “sincerity and frankness.” After Dulles and fellow U.S. statesman Norman Davis returned to the Adlon, their luxury hotel across from the Brandenburg Gate, Davis was unnerved to find the word “Juden” scrawled crudely on the door of his room, even though he was not Jewish. “The conditions are not quite as bad” as anxious reports about Hitler would indicate, Dulles nonetheless wrote Foster from Germany.[Very easy to see why Project Paperclip came about DC]
https://exploringrealhistory.blogspot.com/2019/02/part-1-devils-chessboard-allen.html