A modification of the papal Bull of Demarcation issued in 1493 by Pope Alexander VI, the Treaty of Tordesillas (June 7, 1494) divided the recently discovered New World between its two signatories, Spain and Portugal.
The treaty created an imaginary pole-to-pole meridian in the Atlantic Ocean 370 leagues west of the Cape Verde Islands, granting all lands west of the demarcation line to Spain, and all lands east of it to Portugal.
In this era of uncertain geographic knowledge, both sides recognized that the division was imprecise and unlikely to prevent future conflict. Spain reckoned that the newly discovered Indies (Caribbean) fell well within its sphere of dominion, while Portugal was mainly interested in securing its sea route to Asia around Africa’s Cape of Good Hope.
Notably, the treaty was concluded six years before the Portuguese, under Pedro Álvares Cabral, discovered Brazil (1500), though once Brazil was on the map, there was little doubt that the land fell under Portugal’s jurisdiction.
Thornier problems arose once it became clear that the Indies (Americas) lay between Europe and Asia, a fact that became clear after Portuguese navigator Vasco de Gama’s journey to India and back in 1497–99, Spanish explorer Vasco Núñez de Balboa’s discovery of the Pacific Ocean in 1513, and Portuguese navigator Ferdinand Magellan’s journey to the Pacific around the southern tip of South America in 1520 in the service of Spain. In the wake of these advances in Europe’s knowledge, Portugal refused to abide by a treaty that essentially granted all of Asia to its Iberian rival.
Thus, following a series of armed conflicts in the Moluccas and elsewhere in the Pacific, the Treaty of Tordesillas was modified in 1529 in the Treaty of Zaragoza, which continued the meridian established in 1494 onto the other side of the globe, to a position of 145 degrees east.
Still, the reality remained that military might effectively determined who got what—illustrated for example by the case of the Philippines, which clearly fell within Portugal’s sphere, yet the Spanish first colonized and refused to relinquish until the United States took the island-colony in 1898.
Seen in a broader context, the Treaty of Tordesillas represents the earliest instance of European powers’ carving up the globe among themselves in pursuit of their own domestic, strategic, and imperial designs, a tradition that continued well into the 19th century and after.