With the destruction of the Hungarian Soviet Republic in 1919 he fled to Vienna,[3] where he adopted the pseudonym "Johann Lorenz Schmidt", from the 18th-century Protestant dissident theologian.
Radványi gathered faculty members such as Georg Lukács and Bertolt Brecht, and speakers such as Albert Einstein, who in 1931 hosted a conference titled "What a worker must know about the Theory of Relativity".
The family did not leave France until 24 March 1941, after they had received a transit visa from the United States; they arrived in New York on 16 June 1941.
The SS Monterey's manifest of passengers also included the French anthropologist Claude Lévi-Strauss and surrealistic writer André Breton for New York City and the port of Veracruz, in the Gulf of Mexico.
In Mexico City, the family had an audience in the National Palace with the new president, General Manuel Ávila Camacho.
Vicente Lombardo Toledano, the leader of the Mexican labor movement, asked Radványi to join the recently created Universidad Obrera de México (Workers' University of Mexico) and teach Marxist history and economics.