He then joined the Social Democratic Party (SPD), where he worked under Rudolf Hilferding at the legendary journal, Society, and finished his dissertation in 1932 on “The Proletariat Before 1848.” He would remain a libertarian socialist for the rest of his life.
By the end of 1933, Pachter had been forced to flee to Paris where he took odd jobs, taught at the Universite Populaire, agitated for creating a “popular front” of all antifascist forces, and ultimately served as a publicist for the POUM, a mixed group of Trotskyist and socialists that served the loyalist cause during the Spanish Civil War.
Briefly a member of the anti-Nazi underground in which he helped edit probably the first resistance journal, Proletarian Action, he wound up in the Gurs prison camp, before coming to the United States in 1940.
Soon enough he was working for the Office of Strategic Services, and part-time for the Institute for Social Research at Columbia University, before becoming a founding member of Dissent and entering the academy.
Henry Pachter understood Marxism as a critical method capable of questioning its political employment from a historical and materialist standpoint that emphasized the ability of the working class (rather than a party) to control its destiny.