As his father's only legitimate son, Afonso was the rightful heir to the Portuguese throne. However, he was not, according to several sources, Dinis' favourite son; his half-brother, the illegitimate Afonso Sanches, enjoyed full royal favour. From early in life, the notorious rivalry led to several outbreaks of civil war. In 1325, Afonso IV became king and took full revenge on his brother. His rival was sentenced to exile in Castile, and stripped of all the lands and fiefdoms donated by their common father. Afonso Sanches, however, did not sit still. From Castile, he orchestrated a series of attempts to usurp the crown for himself. After a few failed attempts at invasion, both brothers signed a peace treaty, arranged by the Queen Isabella.
In 1309, Afonso IV married princess Beatrice, daughter of King Sancho IV of Castile by his wife Maria de Molina. The first-born of this union, princess Maria of Portugal, married King Alfonso XI of Castile in 1328, at the same time that Afonso IV's heir, Peter, was promised to another Castilian princess, Constance. These arrangements were imperiled by the ill will of Alfonso XI of Castile, who was, at the time, publicly mistreating his wife. Afonso IV was not happy to see his daughter abused, and started a war against Castile. Peace arrived four years later, with the intervention of princess Maria herself. A peace treaty was signed in Seville in 1339 and, in the next year, Portuguese troops played an important role in the victory of the Battle of Salado over the Marinids Moors in October 1340.
The last part of Afonso IV's reign is marked not by open warfare against Castile, but by political intrigue. Civil war between King Peter I of Castile and his half-brother Henry of Trastamara led to the exile of many Castilian nobles to Portugal. These immigrants immediately created a faction among the Portuguese court, aiming at privileges and power that, somehow, could compensate what they lost at home. The faction grew in power, especially after Ines de Castro, daughter of an important nobleman and maid of princess Constance of Castile, became the lover of her lady's husband: Peter, the heir of Portugal. Afonso IV was displeased with his son's choice of lovers, and hoped that the relationship would be a futile one. Unfortunately for internal politics, it was not. Peter was openly in love with Ines, recognized all the children she bore, and, worst of all, favoured the Castilians that surrounded her. Moreover, after his wife's death in 1349, Peter refused the idea of marrying anyone other than Ines herself.
The situation became worse as the years passed and the aging Afonso IV lost control over his court. Peter's only male heir, future king Fernando of Portugal, was a sickly child, while the illegitimate children sired with Ines thrived. Worried about his legitimate grandson's life, and the growing power of Castile within Portugal's borders, Afonso IV ordered the murder of Ines de Castro in 1355. He expected his son to act reasonably, but the heir was not able to forgive him for the act. Enraged at the barbaric act, Peter put himself at the head of an army and devastated the country between the Douro and the Minho rivers before he was reconciled to his father in early 1357. Afonso died almost immediately after, on May 12.
As king, Afonso IV is remembered as a soldier and a valiant general, hence the nickname the Brave. But perhaps his most important contribution was the importance he gave to the Portuguese navy. Afonso IV granted public funding to raise a proper commercial fleet and ordered the first maritime explorations. The Canary Islands (today a part of Spain) were discovered during his reign.
Afonso's descendants
| Preceded by: D. Diniz |
List of Portuguese monarchs | Succeeded by: D. Pedro I |