Born in 1500, Charles Habsburg's destiny awaited him in the year 1515. Upon the death of Ferdinand of Aragon, fate beckoned him from his home city of Ghent in Flanders to travel south past his enemy-in-waiting France, finally to arrive in Castile. When he arrived in the land to take up his inheritance, his subjects did not take immediately to the awkward seventeen year-old whom they were to call Majestad. Many harboured doubts about whether it was God's will for him to sit upon the throne while his mother, Joanna the Mad, still lived. Joanna famously kept the head of her long-dead husband (whom history has labelled Philip the Handsome) as a courtier for a full ten years after his death, and Charles and his entourage set about governing their new land with no reference to her (or, presumably, the head).
The power and influence of this entourage of Burgundian advisors did not stick well with the Spanish people, who were immediately suspicious of their language and customs. It is reported that almost as soon as their arrival they set about the age-old business of corruption, selling the interests of the native Spaniards for their own wealth and affluence. Hence it is not surprising that the Spanish people feared this apparently foreign King would sacrifice their interests to his wider concerns (Charles possessed a great Empire across Christendom, comprising of the Burgundian Lands, Italy, the New World and Spain).
And in the first few years of Charles' reign, their fears appeared to be taking form. The Cortes (parliament) of Castile and the Cortes of Aragon greeted the new King with rudeness, informing him that he was in their service; but at least they did accept his rule, and issued an initial monetary grant (a servicio). However, fearing the degradation of their fueros (traditional rights), they made Charles promise that in his absences he would not appoint a foreigner to govern them.
Charles was soon to break this promise. His ancestors had traditionally held the position of Holy Roman Emperor, a position which was not hereditery but elective. When the position became vacant upon the death of his paternal grandfather Maximilian I, Charles wished to waste no time in securing the position for himself. Again the Spanish people were riled as their ruler sought to expand his territories and obligations, presumably at their expense. Charles convened the Cortes of Castile to a remote location, where be bullied them into granting another servicio. He would use this money to bribe the electors for the title of Holy Roman Emperor, the traditional and respected method of obtaining the position.
Charles left the Iberian peninsula in 1520 to travel around the electorships and deliver his Spanish money to German princes. Perhaps not aware of the consequences his action would have, Charles appointed Adrian of Utrecht as regent in his absence. Adrian was one of the Burgundians that had travelled with Charles at the start of his reign, and the Spaniards were none too pleased at having the promise of not being subjected to foreign government broken. After only a few months, the major towns in Castile were up in revolt. They formed a league, known as the Communeros, which opposed Habsburg rule. They turned their wrath to the Crown's officials, expelling them and refusing to pay their taxes towards the servicio.
And so it might have continued, with Charles in absentia and the nobility initially unwilling to turn their might against the Communeros. However, as the leaders of the towns grew more confident, their ideas for reform grew more extreme, and it was not long before the Castilian nobility began to feel threatened - in 1521, the nobility put down the rebels at the Battle of Villalar. Such was not done for love of Charles Habsburg, but for love of their own position. Charles soon realized the importance of the nobility in his security, and he was careful throughout his reign to irk them little - never did he think to encroach on their exemption from taxation.
So it was that Charles returned to a Spain in 1522 that was much more unified and stable than the one he had left. Never again would Charles be threatened by an army composed of his own subjects - such was left to his son, who was broken by the Dutch Revolt decades later. The period of Charles' reign 1522-56 (when he abdicated) was tranquil and uninteresting. Indeed, it has been remarked that it seemed Spain had no internal history at all during this period. As he reached manhood the boy King grew in stature and charisma, and he achieved the adoration of his subjects. He did not irk his subjects by intervening unduly in their affairs - the nobles of Aragon retained their right to wage war at will, and the relative poverty of the place did not give him much reason to encroach on their fueros.
Spain, and Castile in particular, became the heartland of Charles' Empire. It was a rich land, and Charles needed immeausurable riches to fight the many wars his Imperial and religious commitments brought to him - against the Valois dynasty of France, the German Protestants and the Ottoman Empire. In Charles' reign France proved itself the trojan horse of Christendom, allying with the infidel Turk to further its own ends in a dynastic feud. Charles, forever the chivalrous knight, challenged Francis I of France to a duel following him breaking provisions of the Treaty of Madrid, as dictated by already outdated feudal custom. This pious, brave and dedicated man was to usher in a Golden Age for Spain, and the Spanish people were justified in looking back gladly at the failure of the Communeros.
As a note of esoterica, Charles' full list of titles ran as follows: "Roman King, future Emperor, semper augustus, King of Spain, Sicily, Jerusalem, the Balearic Islands, the Canary Islands, the Indies and the mainland on the far shore of the Atlantic, Archduke of Austria, Duke of Burgundy, Brabant, Styria, Carinthia, Carniola, Luxembourg, Limburg, Athens, and Patras, Count of Habsburg, Flanders and Tyrol, Count Palatine of Burgundy, Hainault, Pfirt, Roussillon, Landgrave of Alsace, Count of Swabia, Lord of Asia and Africa."
He is most commonly known as "Emperor Charles V."