Portugal and Castile conclude the Treaty of Alcáçovas, ending the War of the Castilian Succession and allocating Atlantic navigation and overseas zones of influence—an important precursor framework to later Tordesillas-based disputes.
Pope Alexander VI issues the bull Inter caetera, granting Spain rights to lands west and south of a specified line; Portuguese اعتراض to this papal allocation helps drive bilateral negotiations culminating in Tordesillas.
Spanish and Portuguese representatives sign the Treaty of Tordesillas, shifting the demarcation line to 370 leagues west of Cape Verde and formalizing competing imperial “spheres” that would be contested in later diplomacy and frontier conflicts.
Pope Julius II issues Ea quae pro bono pacis, providing papal approval and ratification for the Treaty of Tordesillas—reinforcing its status as a Catholic-international settlement (even as practical disputes persisted).
Portuguese and Spanish delegations convene the Junta of Badajoz–Elvas to locate the Tordesillas antimeridian and decide sovereignty over the Spice Islands; the talks highlight measurement limits and fail to yield a binding technical consensus.
Portugal and Spain sign the Treaty of Zaragoza (Saragossa), addressing the Moluccas dispute by defining an opposite-side demarcation (an antimeridian arrangement) and easing a major flashpoint created by competing Tordesillas interpretations in Asia.
Spain recognizes the sovereignty of Portugal’s Braganza dynasty in the Treaty of Lisbon, resetting Iberian relations after the Restoration War and creating new conditions for negotiating (and contesting) colonial frontiers beyond Tordesillas in practice.
Portugal establishes Colonia del Sacramento opposite Buenos Aires, a strategic and commercial foothold that becomes a recurring diplomatic and military dispute-point between the Iberian empires in the Río de la Plata region.
Following Spanish seizure of Colonia del Sacramento, Spain and Portugal sign the Provisional Treaty of Lisbon, which restores the settlement to Portuguese control—an early example of repeated negotiated reversals on a contested frontier.
Spain and Portugal sign the Treaty of Madrid, abandoning Tordesillas/Zaragoza as the operative legal basis for American division and instead using uti possidetis and “natural boundaries” to define extensive limits—crucial to later Brazil-border shape and disputes over exchanges such as Sacramento and the Seven Missions.
Armed conflict breaks out as Guaraní communities in seven Jesuit missions resist forced relocation required by implementation of the 1750 Treaty of Madrid, demonstrating the gap between Iberian diplomatic bargains and realities on the ground.
Spain and Portugal sign the Treaty of El Pardo, repealing the 1750 Treaty of Madrid after demarcation difficulties and the Guaraní conflict—reopening questions that would later be re-addressed by subsequent settlements.
Treaty of Tordesillas disputes and Iberian diplomatic negotiations (1494–1750)
