The Iberian Union refers to the dynastic union of the crowns of Spain and Portugal under the rule of the Spanish Habsburg monarch, Philip II. This union lasted from 1580 to 1640 and was a consequence of a complex series of events, including a succession crisis in Portugal.

Key points about the Iberian Union:

1. Succession Crisis in Portugal (1580):
   • The crisis began with the death of the Portuguese King Sebastian I in 1578 without leaving an heir. His death in the Battle of Alcácer Quibir led to a succession dispute in Portugal.
2. Philip II’s Claim:
   • Philip II of Spain, who was the son of Charles V and already the king of Spain, claimed the Portuguese crown through his mother, Isabella of Portugal, who was the daughter of Manuel I of Portugal.
3. Accession of Philip II (1580):
   • The Portuguese nobility initially resisted Philip II’s claim, but he eventually secured his position as Philip I of Portugal in 1580, thereby establishing the Iberian Union.
4. Habsburg Monarchy:
   • With the Iberian Union, Philip II ruled over a vast empire that included territories from the Americas to Asia. The union created a personal union of the crowns, but the two kingdoms maintained separate administrative and legal systems.
5. Challenges to the Union:
   • The Iberian Union faced various challenges, including resistance from the Portuguese nobility and tensions between Spanish and Portuguese interests. There were concerns about the centralization of power in Madrid and the impact on Portugal’s autonomy.
6. War of Portuguese Restoration (1640–1668):
   • The Iberian Union came to an end in 1640 when a Portuguese revolt led to the restoration of Portuguese independence. John IV of Portugal was proclaimed king, marking the beginning of the House of Braganza. The War of Portuguese Restoration ensued between Portugal and Spain.
7. Treaty of Lisbon (1668):
   • The conflict was resolved with the signing of the Treaty of Lisbon in 1668. The treaty recognized Portugal’s independence, and the Spanish Habsburgs formally acknowledged the rule of the House of Braganza.
8. Legacy:
   • The Iberian Union is often remembered as a period of political and cultural connection between Spain and Portugal. It had lasting effects on the two nations, contributing to mutual influences in various aspects, including art, architecture, and language.
9. Impact on Colonial Empires:
   • The union had implications for the colonial empires of both Spain and Portugal. It influenced colonial administration, trade, and cultural exchanges in regions such as Latin America and Africa.

The Iberian Union is a significant historical episode that shaped the destinies of Spain and Portugal during the late 16th and early 17th centuries. The subsequent restoration of Portuguese independence marked a critical turning point in European geopolitics.