With his newly consolidated place in the nobility of Portugal, Afonso commenced what would be a highly successful political and social career. In 1415 he took part in the Conquest of Ceuta, alongside his father, his brothers, and the leading members of the nobility and military. By the time of his father's death in 1433, Afonso had won favour with his brother, King Duarte I and the rest of high Portuguese society. With his brother's premature death in 1438, a regency was established for Afonso's nephew, the 6 year old King Afonso V, under the leadership of the king's mother, Leonor of Aragon, and later Afonso's brother, Infante Pedro, Duke of Coimbra. The Duke of Coimbra's regency, however, soon proved unpopular and Afonso quickly became the King's preferred advisor. On 30 December 1442, the Duke of Coimbra, still the King's regent and thus acting in his name, created Afonso as the Duke of Braganza, as a gesture of good will and reconciliation between the two brothers. Afonso's elevation to the dukedom, the highest level of nobility, marked the foundation of the House of Braganza, which was to become a key family in Portuguese history.