Revolt of the Brotherhoods
In 1520 and 1521, Castile was distracted by the Revolt of the Comuneros. The Crown of Aragon was also suffering economic difficulties as a consequence of the Revolt of the Brotherhoods. As a result, Spain was seen as a target of opportunity by the King Francis I of France. Meanwhile, the young King Henry II of Navarre, based in Béarn, saw a way to reconquer Navarre. Taking advantage of the synergies with France, Henry began raising a 12,000-strong army, mainly Gascons and Navarrese exiles. This Franco-Navarrese army was commanded by General Asparros (or Esparre). It consisted of 12,000 infantry, 800 mounted knights, and 29 pieces of artillery.