In the Italian Peninsula, the defiant attitude of Popes Gregory II and later Gregory III on behalf of image-veneration led to a fierce quarrel with the Emperor. The former summoned councils in Rome to anathematize and excommunicate the iconoclasts (730, 732); in 740 Leo retaliated by transferring Southern Italy and Illyricum from the papal diocese to that of the patriarch of Constantinople. The struggle was accompanied by an armed outbreak in the exarchate of Ravenna in 727, which Leo finally endeavoured to subdue by means of a large fleet. But the destruction of the armament by a storm decided the issue against him; his southern Italian subjects successfully defied his religious edicts, and the Exarchate of Ravenna became effectively detached from the Empire.