The sixteenth century is traditionally regarded as the age of the break-up of the medieval unity of Christian Europe and of the rise of the new monarchies. To be king of Castile was as good as, being emperor of Germany, and at the first taste of the financial obligations which the new empire imposed on them the Castilian towns rose in rebellion. These three empires were the empire of Charles V, the Ottoman Empire of Selim I and Suleiman the Magnificent, and the Muscovite Empire of Ivan IV, the Terrible. The first and last of these grounded their claims ultimately on their succession to the Roman Empire; and even the second, the Ottoman Empire, did so to a certain extent. But during the first decade of the sixteenth century Shah Ismail Safawi, the ruler of Persia, broke the old tradition of toleration between Sunni majority and Shiite minority in the Muslim world and imposed Shiism on his subjects by force.