He encountered avant-garde art upon visiting the MA gallery of Lajos Kassák and soon contributed to MA under the pseudonym Péter Mátyás.
Following the suppression of the Hungarian Soviet Republic, Kállai went to Berlin but stayed in touch with other Hungarian refugees from the avant-garde art movement in Vienna.
In 1923 he wrote “The Russian Exhibition in Berlin” (Originally published as “A berlini orosz kiállítás”, Akasztott Ember vol. 2 (February 15, 1923)][2]