Charles V revitalized the medieval concept of universal monarchy and spent most of his life defending the integrity of the Holy Roman Empire from the Protestant Reformation, the expansion of the Ottoman Empire, and a series of wars with France. With no fixed capital city, he made 40 journeys, travelling from country to country; he spent a quarter of his reign on the road. The imperial wars were fought by German Landsknechte, Spanish tercios, Burgundian knights, and Italian condottieri. Charles V borrowed money from German and Italian bankers and, in order to repay such loans, he relied on the proto-capitalist economy of the Low Countries and on the flows of gold and especially silver from South America to Spain, which caused widespread inflation. He ratified the Spanish conquest of the Aztec and Inca empires by the Spanish conquistadores Hernán Cortés and Francisco Pizarro, as well as the establishment of Klein-Venedig by the German Welser family in search of the legendary El Dorado. In order to consolidate power in his early reign, Charles suppressed two Spanish insurrections (the Comuneros' Revolt and Brotherhoods' Revolt) and two German rebellions (the Knights' Revolt and Great Peasants' Revolt).