Starting in 1925 and until 1936, Hronek worked as a journalist. From 1936, he was editor at "Central European Radio" in Vienna. Following the annexation of Austria to Nazi Germany in March 1938, he relocated to Paris as correspondent of the publishing house Melantrich. After the occupation of France, he fled to London, where he worked at the Czechoslovak Ministry of Foreign Affairs from 1940 to 1945.