Military conflict in the Revolt of the Comuneros () spanned from 1520 to 1521. The Revolt began with mobs of urban workers attacking government officials, grew to low-level combat between small militias, and eventually saw massed armies fighting battles and sieges. The comunero rebels gained control of most of central Castile quite quickly, and the royal army was in shambles by September 1520. However, the comuneros alienated much of the landed nobility, and the nobility's personal armies helped bolster the royalist forces. The Battle of Tordesillas in December 1520 would prove a major setback for the rebels, and the most important army of the comuneros was destroyed at the Battle of Villalar in April 1521.
This article is arranged geographically, and then chronologically within each region. The royalists tended to maintain the same commanders and armies in each area, with the one major exception of when the Constable of Castile moved out of Burgos to unite with the Admiral and crush the Comuneros at Villalar. The Comuneros leaders switched between regions somewhat more, especially Bishop Acuña, but still maintained regional militias ultimately.
The most important fighting of the war, and where the fighting was mostly by organized armies rather than raiding militia bands, took part in the north-central part of the Meseta—Old Castile, which contained the capital of Valladolid, the temporary capital of both sides Tordesillas, and the stronghold of the Admiral of Castile, Medina de Rioseco. Each of these three cities was highly fortified and sought after. A decent amount of combat took place to the north around Burgos and the Basque country as well, where the Constable of Castile vied against Bishop Acuña's raids and the Count of Salvatierra. The southern part of the Meseta, New Castile, was a bastion of comunero support. The royalists never were able to deploy much in the way of armies here, depending on their allies in the Knights of St. John and the local nobility, but some notable events in the war did take place there. The rest of the country was mostly quiet: Andalusia on the southern coast was almost uniformly pro-royalist, as was Extramadura and Galicia.
Army organization and composition
Comunero forces
The comuneros generally drew their strength from the cities and the urban militias to form their armies. They also aggressively recruited former royal guards who had deserted due to low pay, especially veterans of recent campaigns in Africa such as the Djerba campaign. With the central cities of Castile on their side, no expensive foreign entanglements to fund, and a tendency to loot and repossess property of the opposed nobility, the rebels were well-funded.
However, the lack of noble support meant that cavalry were difficult to find. Additionally, the city dwellers the comuneros recruited often lacked much appreciation for the peasantry, and for some actively looked down upon them. The countryside was initially strongly pro-comunero, but the ravages of the comunero army would eventually cost them some support.
The comunero army also struggled from factionalism from within, and the lack of a clear commander-in-chief. Each militia was generally loyal to its home city first, and only marched with a main comunero army given permission. When Pedro Girón was appointed commander of the army by the Santa Junta, they made it clear that he would only directly control forces recruited by himself and the small army loyal to the Junta. Juan de Padilla withdrew his Toledo militia in protest of losing the appointment. When Padilla later came to take the position, he had better luck in convincing the various militias to follow him, but this was more due to his popularity than his authority.
The need to constantly search out new towns and manors to sack and pillage also made slower or defensive strategies difficult for the comuneros to implement. Whenever the army defended one place and retrenched, some militias would often separate and return home. This would require new recruitment to make up the loss, and thus the army was less experienced than it could have been.