Del Valle, who had been General Douglas MacArthur's commander of artillery during World War II, emerged in the post-war era as an extreme far-right activist and founded of an organization called Defenders of the American Constitution. He was also the primary promoter of John O. Beaty's anti-Semitic book Iron Curtain Over America. This work, which presented anti-Semitic conspiracy theories from disparate sources with a Cold War, anti-communist theme, was very influential on the development of the anti-Semitic right wing of the 1950s and 1960s.
As a result of Del Valle's proselytizing on its behalf, the book was endorsed by a number of other officers including General George E. Stratemeyer, General Charles A. Willoughby, Colonel Truman Smith, General Edward M. Almond and Albert C. Wedermeyer, and received a wide readership among the American far-right.
The book claimed that Jews descended from a medieval Central Asian nation called the Khazars. It argued that a Jewish conspiracy for world domination which originated in this obscure medieval Central Asian nation was the ultimate source of both communism and the international banking system. The book argued that "Khazar Jews" are an "indigestible mass in the body politic" of the countries where they live. It claimed that the Democratic party was completely under the influence of the Khazar conspiracy, and that it was responsible for the formation of the Federal Reserve Bank, United Nations and the State of Israel.
Von Brunn corresponded with Del Valle (read here: Guide to the Pedro A. Del Valle Papers 1949-1978) and said that Del Valle personally gave him a copy of Iron Curtain (read here). Von Brunn credits his anti-Semitism to this book.
According to historian Joseph W. Bendersky, Del Valle believed that the United States was under the control of an "invisible government" of international Jewish bankers. "A Jewish oligarchy had basically run the country for almost half a century, while their fellow conspirators did likewise in Russia and the UN. Del Valle uncovered their influence in Eisenhower's policies, in the NAACP and the civil rights movement, in Supreme Court decisions on desegregation and race mixing, and in the Federal Reserve system. They had maneuvered Truman into prolonging the war with Japan (unnecessarily killing tens of thousands of American boys) and dropping the atomic bomb just so Russia could move into China". (Bendersky, The "Jewish Threat", p. 412)
More on Del Valle here. (Link goes directly to MSWord document.)
UPDATE: Must read: von Brunn's letters to del Valle are digested here.