Portuguese forces, led by King John I and Nuno Álvares Pereira, with support from English longbow men, defeat the Castilians at the Battle of Aljubarrota on August 14, 1385.; ending the 1383–1385 Portuguese crisis and securing its independence from Castile.
The defeat of King John I of Castile prevented the annexation of Portugal and led to the signing of the Treaty of Windsor (1386) between Portugal and England, cementing a long-lasting alliance between the two countries.