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.

The commander of the comunero armies, Juan de Padilla, considered withdrawing to Toro to seek reinforcements in early April, but wavered.

He delayed his decision until the early hours of 23 April, losing considerable time and allowing the royalists to unite their forces in Peñaflor.

Heavy rain slowed Padilla's infantry more than the royalist cavalry and rendered the primitive firearms of the rebels' 1,000 arquebusiers nearly useless.

[2] Padilla hoped to reach the relative safety of Toro and the heights of Vega de Valdetronco, but his infantry was too slow.

According to the account of Pedro de Alcocer (a friend of the Padillas), the Comuneros were betrayed; the artillery and some 300 soldiers had been bought off by the royalists prior to the battle, and switched sides.

[citation needed] The cavalry charges scattered the rebel ranks thus ending the battle and becoming a slaughter.