After the fall of the African Exarchate in the 7th century, caused by the Arab conquest of Carthage, the "ducatus" was directly dependent on Constantinople. It became then an "archontate"; that is, a region with the same characteristics of a "theme" but smaller and less rich. The governors of the island originally held the rank of "hypatos" and later that of "protospatharios", before receiving the title of "patrikios" from the middle of the ninth century. At this time the relations with Byzantium, if not completely interrupted, had become intermittent, however. Due to Saracen attacks, in the 9th century Tharros was abandoned in favor of Oristano, after more than 1,800 years of human occupation while Caralis was abandoned in favor of Santa Igia; numerous other coastal centres suffered the same fate (Nora, Sulci, Bithia, Cornus, Bosa, Olbia among others.). Contacts between Sardinia and the Byzantine empire didn't cease, however, as suggested by the mention of Sardinian imperial guards in Costantine VII's work "De Caereimoniis" (956-959 AD)  The Sardinian "archon" had both military and civil functions. During the period of direct Byzantine rule these were delegated to two different officers, the "dux" and the "praeses". The office of "archon" became the prerogative of a specific family who transmitted the title in succession from father to a son. At the beginning of the 11th century there was a single "archon" for the whole island. This situation changed over the following decades; the first unequivocal attestation of the existence in Sardinia of four separate kingdoms is in the letter of October14, 1073 that Pope Gregory VII (1073–1085) sent from Capua to Orzocco of Cagliari, Orzocco d'Arborea, Marianus of Torres and Constantine of Gallura. During the early Giudicati era the Giudicato of Cagliari were direct descendants of the former Archontate of Sardinia. They helped many Byzantine institutions, including the Byzantine Greek language, to survive. By the end of the century Greek had been supplanted by Medieval Latin and Sardinian. The Sardinian Church followed the Eastern Rite, in which baptism and confirmation were imparted together. Baptism was carried out by submersion in tanks where water came to the knees of the catechumens.