Spain's Gradual Decline Timeline By DianeLewis 1580 1580- The Iberian Union of the crowns of Aragon, Castile and Portugal was established. 1585 1585- Anglo–Spanish War (1585): The war began. Aug 8, 1588 1588- The Spanish Armada was defeated in the English Channel. 1598 1598- Philip III of Spain was crowned. 1604 1604-Anglo-Spanish War (1585): The war ended. 1618 1618- Thirty Years' War: The war began. 1648 1648- The Treaty of Westphalia was signed. 1778 1778- American Revolutionary War: Spain supported the United States. Apr 25, 1898 1898- Spanish–American War: The war began. Aug 12, 1898 1898-Spanish–American War: The war ended.