King Philip II of Spain faced many challenges in ruling his vast empire in the 16th century. While he maintained Catholic unity and controlled the Church, the financial costs of defending the empire and fighting heresy led to government paralysis by the 1590s. Several provinces rebelled due to economic issues and military defeats against France, England, and the Dutch weakened Spanish power. By the end of Philip's reign, the seeds were sown for Spain's later decline, though he did unify the Iberian Peninsula and achieve some cultural and military successes for Spain.