Acclamation
On 6 April 1385, the Council of the Kingdom (the Portuguese Cortes) met in Coimbra and declared John, then Master of Aviz, King of Portugal. This was followed by the liberation of almost all of the Minho in only two months, on the war against Castile and its claims to the Portuguese throne. Soon after, the King of Castile again invaded Portugal with the purpose of conquering Lisbon and removing John I from the throne. John I of Castile was accompanied by French allied cavalry while English troops and generals took the side of John (see Hundred Years' War). John I and Nuno Álvares Pereira, his loyal Constable and talented supporter, repelled the attack on the decisive Battle of Aljubarrota (14 August 1385), where the Castilian army was virtually annihilated. John I of Castile then retreated. The Castilian forces abandoned Santarém, Torres Vedras, Torres Novas, many other towns were delivered to John I by Portuguese nobles from the Castilian side and the stability of the Portuguese throne was permanently secured.
On 11 February 1387, John I married Philippa of Lancaster, daughter of John of Gaunt, who had proved to be a worthy ally, consolidating the Anglo-Portuguese Alliance that endures to the present day.
Read more about this topic: John I Of Portugal