In the earliest history of the diocese,
Ferdinando Ughelli reports the existence of a Saint Petreius, Bishop of Mariana and martyr, for whom a shrine was built by a certain Ugo Colonna of Rome, according to the
Sacra Corsicae Chronica of Salvatore Vitale. Giuseppe Cappelletti points out that Vitale is the only source of the story, but that Ugo Colonna built the Cathedral, which was dedicated to the Assumption of the Virgin Mary, and that San Petreio was a different church. He also notes that the Martyrologies do not report the existence of a bishop, a bishop and martyr, or just a martyr named Perseo or Petreio. Pius Gams both italicizes the name
Perseus and puts it in parentheses, indicating grave suspicion. Ughelli then reports the existence of a Bishop
Catanus, Corsicanus episcopus, who attended the Synod of Arles in 314. Neither the name nor the diocese of Mariana occurs, however, in the list of those who attended the Synod. Ughelli thirdly reports the existence of Bishop Leo of Corsica, on the authority of letters of
Pope Gregory I and the
Sacra Corsicae Chronica of Salvatore Vitale. Bishop Leo did exist, but Pope Gregory addresses him as
episcopus in Corsica, bishop in Corsica, not bishop of Corsica. Leo had been sent by the Pope as an Apostolic Visitor, since, as the Pope notes, the dioceses of Corsica had long been vacant. The fourteenth century was a period of extreme crisis in Corsica. Roger Caratini notes that the population of ordinary people on the island had decreased by 8% between 1300 and 1350, mostly by migration to the territory of Pisa; then came the Black Death; between 1350 and 1400 the population decreased another 19%. The ability to maintain traditional institutions in the face of the new Genoese overlords was greatly compromised. In 1453
Pope Nicholas V entered into a verbal agreement with the
Republic of Genoa, which specified that, although the Pope maintained the exclusive right to appoint bishops on the Island of Corsica, he would appoint only Genoese subjects who were acceptable to the Government. The Genoese government turned the island over to the administration of the Genoese Banco di S. Giorgio, under new statutes for Corsica were issued, the
Capitula Corsorum, which specified that bishops on the island had to be natives of the island. In 1464, however, the Republic of Genoa came under the domination of the
Duchy of Milan, and it was the Milanese who decided appointments. In 1479 the Milanese were compelled to evacuate Corsica, and their regulations were nullified. In 1563, considering the extreme poverty of the diocese of S. Pietro de Accia, which could no longer support a bishop,
Pope Pius IV joined the diocese with the diocese of Mariana, with the new title of Bishop of Mariana and Accia. During the
French Revolution, the
National Constituent Assembly reformed the Church in France, drawing up the
Civil Constitution of the Clergy (12 July 1790). All clergy were obliged to swear an oath of allegiance to the Constitution, thereby effectively entering into a schism with the Papacy and the Roman Catholic Church. The number of bishoprics in France was dramatically reduced. The five bishoprics on the island of Corsica were suppressed and combined into one, to be called the
diocèse de Corse. When the electors of Corsica assembled, they elected Ignace-François Guasco, Provost (or Dean) of the Cathedral Chapter of Mariana as their 'Constitutional Bishop'. The canonical bishop Verclos made his protest and fled to the mainland of Italy. Guasco was consecrated at Aix on 16 June 1791 by Constitutional Bishop Charles-Benoît Roux, Metropolitan of Bouches-de-Rhône; the consecration was valid but illicit and schismatic. On 11 August 1793, judging that the territory of
Corse was too large, the
National Convention in the Constitution of 1793 divided both the department and the diocese of
Corse into two, Golo (Guasco, resident at Ajaccio) and Liamone, and ordered a second bishop to be elected for the northern and eastern part of the island. Before this could be done, however, the British seized the island, and on 23 December 1793, Guasco recanted and resigned. Bishop Verclos immediately returned to Corsica. In November 1801, the decision was taken by Pope Pius VII in implementing the
Concordat of 1801 not to alter the situation in Corsica which had been imposed by the French Revolution. All of the dioceses remained suppressed, with the exception of Ajaccio, which had been the center of the 'Constitutional Bishop of Corse' and which was coincidentally the birthplace of the First Consul, Napoleon Bonaparte. In April 2002 the title
Bishop of Mariana in Corsica (though not the diocesan apparatus) was revived. It has been used to qualify a priest as an auxiliary bishop, and to reward a domestic prelate in the Papal Household. The titular see of Accia was separately revived in 1968. ==Bishops==