An interregnum and a war of succession began in the Kingdom of Portugal in 1383 when King Ferdinand I died leaving no sons and ended when King John I was crowned in 1385 after his victory during the Battle of Aljubarrota.
The Portuguese interpret the era as their earliest national resistance movement to counter Castilian intervention, and Robert Durand considers it as the "great revealer of national consciousness".
John I (Portuguese: João [ʒuˈɐ̃w̃]; 11 April 1357 – 14 August 1433), also called John of Aviz, was King of Portugal from 1385 until his death in 1433. He is recognized chiefly for his role in Portugal's victory in a succession war with Castile, preserving his country's independence and establishing the Aviz (or Joanine) dynasty on the Portuguese throne. His long reign of 48 years, the most extensive of all Portuguese monarchs, saw the beginning of Portugal's overseas expansion. John's well-remembered reign in his country earned him the epithet of Fond Memory (de Boa Memória).