In 1935, Arminio Klein (1880-1948) was appointed president of the Jewish community of Rijeka. In June 1940, soon after the beginning of the war, Klein was arrested together with twenty other Jewish men who had become 'stateless'. In fact, according to Italian racial laws of September 1938, "all Jews who acquired Italian citizenship after 1 January 1919 were denationalized. Since Fiume did not become part of Italy until 1924, all Jews in that city were automatically affected".
20 Fiume Jews, Seized in Roundup of "Stateless", Released; 200 in Trieste May Be Freed
Klein was released after spending two weeks in prison, and on 8 July 1940 he compiled a list of the Judaica of the Great synagogue, that was also signed by the community's secretary Francesco Cantoni. According to Italian historian Silvia Bon, the list was made up in response to a request (soon halted by the Italian Ministry of Interior) by the chief rabbi of Palestine that all Judaica be sent to Jerusalem.
At the end of May 1943, Klein informed the Union of the Italian Jewish Communities that there was a possibility the Great synagogue would be requisitioned for use as a military hospital. However, the requisition of places of worship was forbidden by Royal Decree no. 1741 of 18 August 1940 (Norme per la disciplina delle requisizioni), which included rules for managing requisitions. The Great synagogue complex also hosted the community offices, the local headquarters of Jewish charities, the historical and current archives, and the Jewish secondary school (letter dated 24 May 1943).
Letter from Arminio Klein to the Union of the Italian Jewish Communities, 24 May 1943