He opened his reign by a very astonishing victory. He led his troops into Italy over a pass which had hitherto been regarded as impracticable for cavalry, and defeated the Swiss--who were in the pope's pay--at Marignano. He then occupied Milan and opened negotiations with Leo X, who was glad to make terms with the victorious young king. The pope agreed that Francis should retain Milan, and Francis on his part acceded to Leo's plan for turning over Florence once more to the Medici. This was done, and some years later this wonderful republic became the grand duchy of Tuscany, governed by a line of petty princes under whom its former glories were never renewed.[260] [Sidenote: Sources of discord between France and the Hapsburgs.] Friendly relations existed at first between the two young sovereigns, Francis I and Charles V, but there were several circumstances which led to an almost incessant series of wars between them. France was clamped in between the northern and southern possessions of Charles, and had at that time no natural boundaries. Moreover, there was a standing dispute over portions of the Burgundian realms, for both Charles and Francis claimed the _duchy_ of Burgundy and the neighboring _county_ of Burgundy--commonly called Franche-Comté. Charles also believed that, through his grandfather, Maximilian, he was entitled to Milan, which the French kings had set their hearts upon acquiring. For a generation the rivals fought over these and other matters, and the wars between Charles and Francis were but the prelude to a conflict lasting over two centuries between France and the overgrown power of the house of Hapsburg. [Sidenote: Henry VIII of England, 1509-1547.] In the impending struggle it was natural that both monarchs should try to gain the aid of the king of England, whose friendship was of the greatest importance to each of them, and who was by no means loath to take a hand in European affairs. Henry VIII had succeeded his father (Henry VII) in 1509 at the age of eighteen. Like Francis, he was good-looking and graceful, and in his early years made a very happy impression upon those who came in contact with him. He gained much popularity by condemning to death the two men who had been most active in extorting the "benevolences" which his father had been wont to require of unwilling givers. With a small but important class, his learning brought him credit. He married, for his first wife, an aunt of Charles V, Catherine of Aragon, and chose as his chief adviser Thomas Wolsey, whose career and sudden downfall were to be strangely associated with the fate of the unfortunate Spanish princess.[261] [Sidenote: Charles V goes to Germany.]