From 1932 to 1935, he was a correspondent of the Polish Telegraphic Agency in Moscow, but was expelled in 1935. He used the experience gathered during his stay in the USSR in his books: Nowa Rosja. Na przełomie dwóch piatiletek [“New Russia. Between Two Five-Year Plans] (1933–1934), Minus Moskwa (Wołga – Kaukaz - Krym) [“Minus Moscow (Volga–Caucasus–Crimea)”] (1935), Kreml na biało [“Kremlin in White”] (1936), Sowieckie zbrojenia moralne [“Soviet Moral Armaments”] (1937). His descriptions of Soviet reality were highly popular but also often criticised (e.g. by Jerzy Niezbrzycki who wrote under the pen name Ryszard Wraga (1902–1968) – a Sovietologist who published, among others, in Bunt Młodych in the interwar period) as simplistic and naïve. During World War II, Berson managed to leave Poland and travelled to Scandinavia via Lithuania. He was a correspondent during the Finnish-Soviet War.