[2] He chose an ecclesiastical career, and on 19 August 1365 the Venetian Senate recommended him for the position of Latin Archbishop of Patras in the Morea in southern Greece.
For the remainder of the century, the Archbishops of Patras played an active role in the intrigues and feuds of the Principality, and in turn the contending families often tried to place one of their own scions on the archiepiscopal throne.
The civil authorities in Venice vehemently opposed the tithe, and forbade it outright on 29 August 1368, leading to a complete breakdown of relations between the Republic and the Church, as Popes Urban V and Gregory XI backed Foscari.
[10][11] The failure of the Hospitaller enterprise inaugurated a period of turmoil for Achaea, complicated by the arrival of the mercenary Navarrese Company and the effects of the Western Schism between Pope Urban VI and Antipope Clement VII.
Achaea passed under the control of titular Latin Emperor James of Baux, who appointed the leader of the Navarrese Company, Mahiot de Coquerel, as his bailli.
As a result, Urban VI confiscated the Principality of Achaea and on 6 September 1387, Foscari was appointed vicar-general on behalf of the Pope, and authorized to hire the Navarrese Company on his own account.
Likewise another pretender, Louis II, Duke of Bourbon, who might have rallied the Principality behind him, was caught up in the French expedition against the Barbary pirates in 1390 and abandoned his plans.
[16][17] The long interregnum lasted until 1396, when Mahiot's successor at the head of the Navarrese Company, Pedro de San Superano, received recognition as hereditary Prince of Achaea from King Ladislaus of Naples.