Following the ascension of Afonso V in 1448, the kingdom of Portugal fell into civil war, as tensions between Infante Peter, Duke of Coimbra, and Afonso, Duke of Braganza, erupted into armed conflict.

The Civil War: The Rival Factions

1. Infante Peter, Duke of Coimbra

   • Former regent of Portugal (1439–1448) and uncle of Afonso V.
   • Favored strong royal authority, centralization, and continued overseas expansion.
   • Supported by Lisbon’s merchants, the lower nobility, and the commoners.

2. Afonso, Duke of Braganza

   • Another uncle of Afonso V, representing the old, landowning aristocracy.
   • Opposed Peter’s policies, seeking to increase noble privileges.
   • Manipulated Afonso V into declaring Peter a traitor based on false accusations.

The First Engagement: Victory for Peter at Penela

• Peter’s forces initially defeated Braganza’s army at Penela, showing that he still commanded strong military support.
• However, Afonso V, siding with Braganza, mobilized a massive royal army of 30,000 troops, determined to eliminate Peter as a political threat.

The Battle of Alfarrobeira (May 20, 1449)

• The two armies met near the Alfarrobeira River, at Alverca, north of Lisbon.
• Peter’s forces were vastly outnumbered but fought fiercely.
• The battle was short, and Peter was killed early on—
  • Some sources say he died fighting.
  • Others claim he was assassinated by one of his own men.

Aftermath: The Triumph of the House of Braganza

• Afonso V consolidated power under Braganza’s influence, granting the duke new lands, privileges, and political authority.
• The House of Braganza became the most powerful noble family in Portugal, rivaling even the monarchy.
• Portugal shifted towards a government dominated by the aristocracy, slowing the Crown’s ability to centralize authority.

Long-Term Consequences

1. Weakened Royal Authority – The monarchy remained under noble control, delaying later reforms.
2. Braganza’s Dominance – The House of Braganza amassed vast wealth and influence, eventually challenging the Crown itself.
3. A Prelude to Future Conflicts – The battle set a precedent for noble interference in royal affairs, a trend later reversed by King John II (r. 1481–1495).

The Battle of Alfarrobeira (1449) marked a turning point in Portuguese history, securing the aristocracy’s dominance while eliminating one of Portugal’s most capable leaders, Infante Peter.