Complex sentence: The arrival of large numbers of followers of the Vilna Gaon known collectively as the Perushim was especially notable, but sizeable groups are recorded as arriving from most of the world's Jewish communities, including Persia, Yemen, Morocco, Algeria and Russia.
Split into simpler sentences: The arrival of large numbers of followers of the Vilna Gaon, known collectively as the Perushim, was especially notable. Sizeable groups are recorded as arriving from Jewish communities all over the world, including Persia, Yemen, Morocco, Algeria and Russia.