The Russian Communist leader and publicist Karl Bernardovich Radek (1885-1939) is best known for his brilliant and acerbic polemics. He was an outstanding apostle of internationalism.

Karl Radek was born Karl Sobelsohn in Lvov (then in Austrian Poland) to an Austrophile Jewish family. As a youth, he rejected his family's outlook and became involved in political agitation, moving to Switzerland in 1904. There he joined the left wing of Polish socialism, returning to Poland in 1905 to participate in revolutionary activity in Warsaw. After a brief prison term, Radek spent the next decade building his reputation, in both Poland and Germany, as a talented but volatile and often irresponsible journalist. His barbed comments so irritated leading Socialists that he was successively expelled from the Polish and German Socialist parties.

During World War I Radek returned to Switzerland, where he alternately collaborated with and contended with V. I. Lenin in the...