Power and weakness
The Habsburgs reached the zenith of their power before the end of the 16th century: the duchy of Milan, annexed by Charles V in 1535, was assigned by him to his son, the future Philip II of Spain, in 1540; Philip II conquered Portugal in 1580; and the Spanish dominions in America were ever expanding. There were, however, three faults in the power structure—two of them historical accidents, the third an effect of the Habsburg dynasty’s own measures for self-preservation.
In the first place, the ascendancy of Charles V coincided with the outbreak of the Protestant Reformation in Germany, which was to spread turmoil for decades over Europe from the Netherlands to Hungary. As Charles, from his Spanish upbringing, was imbued with ideas of Catholic uniformity and as his successors, with the exception of the enigmatic Maximilian II, sought also to realize those ideas, religious resistance to the Habsburgs’ authority came to aggravate or to camouflage political resistance. At the same time, the papacy, overawed though it was by the Spanish military presence in Italy, did not always subscribe to the Habsburg’s special policy for Catholicism.
Secondly, Ferdinand’s accession to Hungary meant that the Habsburgs had to bear the brunt of the Ottoman Turkish drive from the Balkans into central Europe, just as Habsburg Spain had to confront Turkish incursions into the western Mediterranean. The great victory of Lepanto (1571), won by Charles V’s natural son, Juan de Austria, did not end those troubles, which were exploited, against the dynasty, by Hungarian dissidents and, more covertly, by France.
The third flaw in the Habsburg edifice was latent in the 16th century. Mindful of what they had won by marriages, the Habsburgs sought to preclude rival dynasties from turning the tables on them by the same means: to keep their heritage in their own hands, they began to intermarry more and more frequently among themselves. The result, in a few generations, was a fatal inbreeding that brought the male line of Charles V to extinction.