The Battle of Aljubarrota, which took place on 14 August 1385 near the village of São Jorge in central Portugal, some 100 km north of Lisbon, was one of the most important events in Portuguese history. It also played a significant role in the Iberian Peninsula as a whole, because it brought the kings of Portugal and Castile (both called John I) face to face, ultimately guaranteeing the independence of the small kingdom of Portugal. Furthermore, less than 30 years after the Battle of Poitiers (1356), Aljubarrota became another example of the ingenious use of the English tactical style that had been developed in the Anglo-Scottish wars of the early fourteenth century and was successfully tested by the armies of Edward III and the Black Prince in the first battles of the Hundred Years War.

Nevertheless, Aljubarrota has attracted relatively little attention from scholars. Sir Peter Russell devoted a chapter to it in a book which remains the most stimulating work on the political and diplomatic history of the Iberian Peninsula in the second half of the fourteenth century. But Russell was not a military historian, and despite his familiarity with Iberian archives and the visit he made to the battlefield, he did not have at his disposal all the relevant information about the combat. For example, an archaeological intervention that took place at the site between 1958 and 1960 (after the publication of Russell's book) uncovered a remarkable defensive system of ditches and pits (built by the Portuguese army with the help of their English allies) and a common grave containing human bones, which recent research has proved to be related to the 1385 battle. This has opened up new lines of inquiry.

For this reason, I believe that it is time to return to the Battle of Aljubarrota and reassess it in the light of this new evidence. For not only do we know the exact spot where the battle took place, but we also have a series of first-rate sources (both literary and non-literary) that converge with an accuracy rarely found in medieval military history.