Charles sought to become leader of a universal empire. His imperial dreams were encouraged by M. A. di Gattinara, whose influence replaced that of Charles's Flemish advisers. The chief problems Charles faced were the Protestant Reformation in Germany; the dynastic conflict with King Francis I of France, particularly for supremacy in Italy; and the advance of the Ottoman Turks.
Shortly after his election Charles began his lifelong struggle with France (see Italian Wars), which required immense expenditures. In 1520 he signed the Treaty of Gravelines with King Henry VIII of England, and in 1521 he invaded N Italy, then controlled by France. The fiscal onus for the war rested on Spain and provoked violent reaction, particularly in Castile, which resented Charles's high-handedness in obtaining funds from the Castilian Cortes. Toledo, Segovia, and other Castilian cities revolted in the brief war (1520–21) of the comuneros. Initially aimed at limiting the royal power, the uprising was later marked by violent class warfare. It was put down at the battle of Villalar; Juan de Padilla and other leaders were executed. Charles later won the loyalty of his Spanish subjects.
In Germany, at the fateful Diet of Worms (see Worms, Diet of) in 1521, Charles secured a satisfactory compromise regarding the Reichsregiment but unyieldingly opposed the doctrines of Martin Luther. In his written opinion, Charles declared himself ready to stake his dominions, friends, blood, life, and soul on the extinction of heresy. Late in May, 1521, he signed the Edict of Worms, outlawing Luther and his followers. However, Charles's preoccupation with the war with France prevented him from checking the spread of Luther's doctrines. Also, Charles was not always supported by the popes, who were concerned with the threat to their temporal power and independence posed by imperial domination of Italy.
After the French defeat at Pavia (1525) and the capture of Francis I, Charles seemed triumphant in Italy; Francis signed (1526) the humiliating Treaty of Madrid, by which he renounced his Italian claims and ceded Burgundy to Charles. On his release, however, Francis repudiated the treaty and organized the anti-imperial League of Cognac. The pope, Venice, Milan, and Florence joined the league. Charles sent an imperial army to Italy composed mostly of German Lutherans. Led first by Georg von Frundsberg and then by Charles de Bourbon, the army defeated the league and then marched on Rome, where the force sacked (1527) the city and besieged Pope Clement VII. Although the "German Fury" was disavowed by Charles, he profited from the outrage, extorting large sums of money from the pope.
The Treaty of Cambrai (see Cambrai, Treaty of) with France and the Peace of Barcelona with the pope (both 1529) confirmed Charles's position in Italy and secured his coronation as Holy Roman emperor at Bologna (1530). Charles was the last German emperor to be crowned by the pope. His brother Ferdinand, king of Bohemia and Hungary (later Holy Roman Emperor Ferdinand I), was elected king of the Romans, or German king, in 1531. Charles, who had awarded Ferdinand the Austrian duchies in 1521, delegated increasing authority to him in Germany, which was then torn by religious and social struggles. The rebellion (1522–23) of Franz von Sickingen was followed by the more serious Peasants' War (1524–26), and the Swabian League in 1531 made way for the Lutheran Schmalkaldic League. The Reformation progressed, and the breach between Catholics and Protestants widened.
Before dealing with the religious problem, Charles had to make peace abroad. Ottoman assaults in Austria and Hungary and along the Mediterranean coast posed a serious threat to the Hapsburg lands. In 1535, Charles launched a successful expedition against Tunis. In E Europe, Ferdinand attempted to hold back the Ottomans. In 1536, war broke out with Francis I over the succession to Milan. Intent on recouping in Italy, Francis allied himself with the Ottoman sultan, Sulayman I. Although a truce ended the fighting with Francis in 1538, the Ottomans continued their assaults on the Italian coast. A second expedition by Charles, this time to Algiers, was unsuccessful (1541). In 1542, Francis, again allied with Sulayman, renewed warfare. Charles joined (1543) with Henry VIII and in 1544 forced Francis to make peace at Crépy.
A subsequent truce with the Ottomans, however humiliating, gave Charles and Ferdinand some respite. At last the way opened for the Counter Reformation, ardently desired by Charles and forwarded by St. Ignatius of Loyola, when the Council of Trent (see Trent, Council of) convened in 1545. Turning on the Protestant princes of Germany, Charles split their ranks by winning over Maurice of Saxony and others, attacked the Schmalkaldic League in 1546, defeated (1547) John Frederick I of Saxony at Mühlberg, and imprisoned Philip of Hesse. At the Diet of Augsburg (1547) he secured the incorporation of the Netherlands into the Hapsburg hereditary possessions and forced through the Augsburg Interim (1548), a compromise profession of doctrine that he then tried to impose on the Protestants with the help of Spanish troops. In 1552, Maurice of Saxony changed sides again, called in Henry II of France, Francis's successor, and even attempted to capture Charles at Innsbruck.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.