Socialists become Communists or Fascists, F.A. Hayek, 1944

"No less significant is the intellectual history of many of the Nazi and Fascist leaders. Everyone who has watched the growth of these movements in Italy or in Germany has been struck by the number of leading men, from Mussolini downward (and not excluding Laval and Quisling), who began as socialists and ended as Fascists or Nazis. And what is true of the leaders is even more true of the rank and file of the movement. The relative ease with which a young communist could be converted into a Nazi or vice versa was generally known in Germany, best of all to the propagandists of the two parties. Many a university teacher during the 1930s has seen English and American students return from the Continent uncertain whether they were communists or Nazis and certain only that they hated Western liberal civilization."

 "The Road to Serfdom; text and documents, The definitive edition," ed. by Bruce Caldwell, (The collected works of F.A. Hayek, vol 2) University of Chicago Press, c1944, c2007. pp. 80-81