This study analyses the presence of Castilian men of arms in the siege and conquest of Balaguer in 1413. It deals with the challenge of James, the Count of Urgell, to King Ferdinand, and how the latter, after virtually suppressing the various centres of support to his opponent, decided to lead the troops and attack Balaguer, where had taken refuge. Essential for this endeavour were the supplies, a large proportion of which were channelled through members of his family or Castilian collaborators. Attention is given to the nature and the places of the supplies, the means and the tactics used. Then, we focus not only on the members of important lineage of high and middle Castilian nobility collected in chronicles, but also on others whose names only appear in archival documents.