Complex sentence: The Jewish community of Fiume, which counted 1,500 individuals, was stranded, as the city had been annexed to Italy only in 1924 and virtually all its residents were subject to the expulsion decree.
Split into simpler sentences: The Jewish community of Fiume, which counted 1,500 individuals, was stranded, as the city had been annexed to Italy only in 1924. Virtually all its Jewish residents were subject to the expulsion decree.