At the beginning of the 16th century, the Crown of Castile was one of the most powerful in Europe; during the first years of the reign of Charles I of Spain, it had to face an uprising known as the War of the Communities. On April 23, 1521, the Battle of Villalar took place, one of the most momentous events in Spanish modern history. That day started the end of a revolt that some of the most important historians have ventured to describe as “the first modern revolution in history: the Revolution of the Communities of Castile.” Why the commoners rebelled before the king and emperor Charles V, what their leaders Bravo, Padilla, and Maldonado intended, and what model of State they were looking for, are some of the questions that have been the subject of study for centuries.