Rezsö Kasztner was born in Cluj (Kolozsvar) in 1906. He was a life long Zionist since his young student days. Although Kasztner studied law, his interest lay in politics. One of the most important activities of the Zionist movement in the 1920s in Cluj was the publication of the daily newspaper, Uj Kelet (New Middle East). Early in his twenties he became the political and parliamentary correspondent of this newspaper. In that capacity he developed a wide acquaintanceship with the Romanian political establishment. Fluent in five languages, Rezsö Kasztner played an important role in aiding the Jewish community in its often difficult interactions with various political factions in Transylvania.

     After the annexation of Transylvania by Hungary in 1940, Kasztner left his hometown of Cluj and moved to Budapest. Together with Joel Brand and Samuel Springmann, he helped create the Relief and Rescue Committee of Budapest in 1942. This organization worked in clandestine cooperation with other rescue efforts in Slovakia and in Istanbul. Through these rescue activities, Kasztner met Oskar Schindler in December of 1942 when Schindler travelled to Hungary to inform the members of the Rescue Committee of Nazi attrocities in Poland.

     In May of 1944, Joel Brand was sent by Adolph Eichmann to Istanbul to attempt to negotiate the ransom of Hungarian Jewry -- "a million Jews for ten thousand trucks." With Brand's departure, Kasztner was left to continue negotiations with various Nazi officials. In July of 1944, a representative of Himmler, Colonel Kurt Becher took over negotiations with Kasztner. Through these negotiations, Kasztner was able to secure the rescue of a "token" transport of 1,684 Jews, plus an additional nearly twenty thousand Jews who were sent to a relatively "safe" work camp in Austria for the duration of the war.

     At the end of World War II, Kasztner was called by the Allies to help identify roles played by various members of the German high command in preparation of the Nuremberg War Crimes Trials.