 Navarre had been invaded by Ferdinand II of Aragon in 1512, and the portion south of the Pyrenees was annexed to Castile in 1515, so becoming a kingdom part of the Crown of Castile.After John III's 1516 failed reconquest attempt, his son and legitimate heir apparent to the throne of Navarre, Henry II, saw an option through to reconquer the kingdom now the Castilian army was busy dealing with the Revolt of the Comuneros.He sent a large French/Navarrese army commanded by General André de Foix, Lord of Lesparre, (or "Asparros" or "Esparre") across the Pyrenees, consisting of 12,000 infantry, 800 mounted knights, and 29 pieces of artillery.