In late March 1521, the royalist side moved to combine their armies and threaten Torrelobatón, a rebel stronghold. The Constable of Castile began to move his troops (including soldiers recently transferred from the defense of Navarre) southwest from Burgos to meet with the Admiral's forces near Tordesillas. This was possible due to the comunero-aligned Count of Salvatierra's force being caught up in the siege of Medina de Pomar; the Count's forces had previously been enough of a threat to force the Constable to maintain a large army to defend Burgos. The Constable's army was approximately 3,000 infantry, 600 cavalry, 2 cannons, 2 culverin, and 5 light artillery pieces. His army took up positions in Becerril de Campos, near Palencia. Meanwhile, the comuneros reinforced their troops at Torre