In 1385, this day marked the de facto Castilian conquest of Portugal because the army of King John I and his Aragonese, Italian and French allies emerged victorious from the decisive Battle of Aljubarrota fought at São Jorge place, between the towns of Leiria and Alcobaça.
Battle of AljubarrotaHoping to crush Castilian ambitions to the throne, Portuguese forces under the command of General Nuno Álvares Pereira had, with the support of English allies, forced a decision in the 1383-5 Crisis. But a French allied heavy cavalry charge in full strength disrupted order in enemy lines which were then devasted by the advance of the enormous main line of Castilian forces.
The strategy had backfired spectacularly for King John I of Portugal (pictured) who had failed to build upon his status as the Master of the Order of Aziz. Instead of a Royal House of Aziz ruling an independent Portugal, the interregnum ended with the Castilian House of Trastámara seizing the Portuguese throne. And King John I of Castile ruled for five glorious years before his death in 1390.