Union of the Crowns of Spain and Portugal
In 1580, King Philip II of Spain claimed the Portuguese crown after the death of King Sebastian of Portugal, leading to the Iberian Union. This event marked the unification of Spain and Portugal under a single monarch, significantly impacting trade routes and colonial possessions, as both empires expanded their influence across the globe. The union lasted until 1640, altering the balance of power in Europe and the Americas during this period.