Complex sentence: In the beginning of 1920s, Soviet authorities initiated a large campaign of persecution and repression against the Russian Orthodox Church--many priests and bishops were arrested and executed, including St. Veniamin, Metropolitan of Petrograd (+1922).
Split into simpler sentences: In the beginning of 1920s, the Soviet authorities initiated the large campaign of persecution and repression against the Russian Orthodox Church. As a result of it, many priests and bishops were arrested and executed, including St. Veniamin, Metropolitan of Petrograd (+1922).