The Battle of Aljubarrota and the Securing of Portuguese Independence (1385)

Following the retreat of Castilian forces, João of Avis seized the opportunity to legitimize his claim to the Portuguese throne. In March 1385, he convened a cortes to resolve the succession crisis.

João I Proclaimed King (April 6, 1385)

• João das Regras, a skilled jurist and political strategist, presented João’s case before the cortes, systematically dismissing the claims of rival pretenders to the throne, including Beatriz of Portugal, wife of Juan I of Castile.
• On April 6, 1385, João was officially proclaimed King João I of Portugal, securing the legitimacy of the House of Avis.
• As a key military decision, João appointed Nuno Álvares Pereira as Constable of Portugal, placing him in charge of the kingdom’s defense.
• At the same time, English longbowmen began arriving in Portugal, reinforcing the Anglo-Portuguese alliance, which had been formalized in the Treaty of Windsor (1386).

Military Campaigns Leading to Aljubarrota

• Nuno Álvares Pereira marched north, securing the submission of Braga, Guimarães, and other strongholds loyal to Castile.
• In response, Juan I of Castile sent an army to attack Viseu, but his forces were routed at Rancoso, where the Portuguese used the same defensive tactics that had won them victory at Atoleiros.
• Despite these setbacks, Juan I remained determined to capture Lisbon and marched south with a massive Castilian force.

The Battle of Aljubarrota (August 14, 1385)

João I and Nuno Álvares Pereira, recognizing the danger of a prolonged siege of Lisbon, chose to engage the Castilian army before it reached the capital. The two armies met on the plain of Aljubarrota, about 60 km north of Lisbon, on August 14, 1385.

Portuguese Strategy and the Devastation of Castile

• The Portuguese army, numbering 7,000 men, faced a Castilian force of 32,000.
• Nuno Álvares Pereira deployed his troops in defensive squares of dismounted cavalry, a tactic inspired by English longbowmen tactics used at Crécy and Poitiers.
• The Portuguese forces built field fortifications and wooden stakes to disrupt Castilian cavalry charges.
• When the Castilian army attacked, the Portuguese held firm, forcing the enemy into disorder and confusion.
• Within thirty minutes, the Castilian army collapsed in complete disarray, suffering enormous casualties, while João I’s forces emerged victorious.

The Aftermath: The Securing of Portuguese Independence

• Although further battles followed, Aljubarrota was decisive, marking the beginning of the end of Castile’s attempt to dominate Portugal.
• Final peace with Castile was not signed until October 1411, but Portugal’s independence had been secured for almost two centuries.
• This victory solidified João I’s rule, ensured the survival of the House of Avis, and paved the way for Portugal’s Age of Exploration and maritime expansion.

The Battle of Aljubarrota remains one of the most significant military victories in Portuguese history, not only securing the kingdom’s sovereignty but also shaping its political and strategic future.