Upon the assassination of his brother
Lucien on 22 August 1523, Augustine was appointed Regent to Lucien's son
Honoré, who was not yet a year old. He held this position for over 8 years, until his death at the age of 50 in 1532. In 1524, to better avenge himself on his brother's murderers, Bartholomew Doria and
Andrea Doria, Augustine deserted
Francis I of France, with whom the Doria's were allied. He then swore allegiance to
Charles V,
Holy Roman Emperor and
King of Spain, by the signing of the Treaties of
Burgos and
Tordesillas. This brought
Monaco under
Spanish protection, and Augustine was placed at the head of the government in
Monaco. The alliance lasted from 1525 to 1641. This alliance weighed heavily on the financial situation of
Monaco, and shortly before his death, Augustine admitted to regret for his actions in this regard. During his Regency,
Charles V paid a visit to
Monaco in 1529. ==Bishop and Abbot==