[1][2] A lawyer, he is known for his neo-Spenglerian book Imperium: The Philosophy of History and Politics, published in 1948 under the pen name Ulick Varange, which called for a neo-Nazi European empire.

[9][4] After legal appointments in Detroit in 1944–45, he worked for eleven months on the War Crimes tribunal in Germany before he either resigned or was fired for siding with the Nazis.

He was also a friend of a German American intelligence officer Herbert Hans Haupt, who stayed at the home of his wife and was later executed for espionage for his participation in Operation Pastorius.

[30] Later, Yockey received an honorable discharge from the Army for "dementia praecox, paranoid type" in 1943 after suffering a nervous breakdown or feigning one.

[22] Evidence suggests Yockey may have tried to help accused Nazi war criminals including SS General Otto Ohlendorf by sharing top-secret documents with German defense lawyers.

[2] Over time, he contacted or worked with far-right figures and organizations including the German-American Bund, the National German-American Alliance, William Dudley Pelley's Silver Shirts, Sir Oswald Mosley's Union Movement, George Sylvester Viereck, the American H. Keith Thompson, Gerald L. K. Smith, and James H. Madole's National Renaissance Party.

[35] Yockey identified the United States, not Russia, as Europe's main enemy, urged Europeans not to collaborate with America in the Cold War, and wanted to act against American forces in Germany and England.

[36][37] Without notes, Yockey wrote his first book, Imperium: The Philosophy of History and Politics, in Brittas Bay, Ireland, over the winter and early spring of 1948.

Imperium is a Spenglerian critique of 19th century materialism and rationalism[38] that scorns democracy and equality, extols Nazism, and blames Jews for various problems.

[22] Views expressed in it were endorsed by former Nazi General Otto Remer (who had been Hitler's bodyguard);[40] the American Revilo P. Oliver; and Italian esotericist Julius Evola,[41] as well as the praise of Hans-Ulrich Rudel, Giorgio Almirante, Heinz Knoke, and Karl-Heinz Priester.

[42] Yockey became embittered with Sir Oswald Mosley (Hitler's leading British proponent[11]) after the latter refused to publish or review Imperium upon its completion, after having promised to do so.

[11] With a small group of British fascists including the former Mosleyites Guy Chesham and John Gannon, Yockey formed the European Liberation Front (ELF) in 1948–49.

[44] It issued a newsletter, Frontfighter, and in 1949 published Yockey's virulent anti-American, anti-communist and antisemitic text The Proclamation of London, which called for a reinstatement of Nazism and the expulsion of the Jews (whom it labeled "the Culture-distorter") from Europe.

[12][22] The American Nazi Party of George Lincoln Rockwell rejected Yockey's anti-American attitude and willingness to work with anti-Zionist communist governments and movements.

Although McCarthy never delivered it as the theme of the speech, when it was announced through posters in the Yorkville neighbourhood of New York City, the-then Left Wing newspaper The Daily Compass ran a front page expose, alongside negative press attention from the New York Post, probably influenced by the fact that a series of well known Holocaust deniers were going to speak alongside him.

[54] In 1957, FBI agents assessed that he was "living in Los Angeles as a pimp or a gigolo" and had written pornography for money, including a sadomasochistic booklet called Arduous Figure Training at Bondhaven that was later found in his suitcase.

[34] The 62-page booklet was published by Nutrix Company of Jersey City and according to the FBI "contained numerous sketeches of partially clad females and [...] was of a masochistic or sadistic nature.

En route to Oakland, California, his suitcase had either been lost or had broken open at the Dallas airport, and authorities found several of Yockey's falsified passports and birth certificates.

He had a greater impact in Europe, in the European New Right, where for instance the Belgian Jean Thiriart[60]and the Frenchmen Christian Bouchet,[61] René Binet, and Dominique Venner are known to have been influenced by him.

[62] Additionally, the Russian philosopher Aleksandr Dugin, and the French writer Alain de Benoist, adopted positions similar to Yockey's, although there is little evidence his work influenced them in this.

[67] According to the American political scientist George Hawley, "Yockey's vision of a global fascist movement that transcends national borders is now a common trope within the Alt-Right".

[37] In his 2011 book of correspondences with American conductor David Woodard, Swiss writer Christian Kracht recommended Yockey's Imperium.

[70] Other terrorists inspired by Yockey include Leo Felton, responsible for the 2002 white supremacist terror plot and John William King an assailant in the Murder of James Byrd Jr.. [71] Additionally, far-right political activist Augustus Sol Invictus has drawn inspiration from Yockey's book Imperium,[72] as well as the New Zealander Kerry Bolton.