Cartographers and Competing Claims

Columbus's voyage on behalf of Spain alarmed Portugal, which believed earlier agreements had granted it exclusive rights to explore south and west of the Canary Islands. Unable to challenge Portugal's naval power directly, Spain's monarchs turned to the pope, who decreed that all lands falling west of a line drawn through the Atlantic belonged to Spain. Portugal negotiated to move this line farther west, and the resulting 1494 Treaty of Tordesillas cut across the eastern bulge of South America, leaving the future territory of Brazil to Portugal while granting Spain the rest of the Americas. This agreement required increasingly skilled cartographers, mapmakers whose work became essential as European monarchs needed accurate charts to understand exactly what they were claiming and dividing.

The dividing line's implications did not stop at the Atlantic. When Portuguese sailors reached India by rounding Africa, and Spanish-funded explorer Ferdinand Magellan's expedition became the first to circumnavigate the globe in 1522 by sailing around South America and across the Pacific, both nations claimed rights to the valuable spice-producing Maluku Islands in modern Indonesia. To settle this new dispute, Spain and Portugal signed the 1529 Treaty of Zaragoza, extending their dividing line into the Pacific Ocean and awarding the Maluku Islands to Portugal. Spain, unable to afford compensating Portugal for the islands, and with the two royal families united by marriage, ultimately abandoned its claim.

Not every European power accepted these agreements. England and the Netherlands, both Protestant nations following the Reformation, felt no obligation to honor decrees issued by a Catholic pope, and France, though it remained Catholic, ignored the treaties in practice as well, with King Francis I reportedly declaring that the sun shines for me as it does for others. As Spain and Portugal's power declined through the seventeenth century, England, France, and the Netherlands expanded freely into territory the two treaties had supposedly reserved for Spain and Portugal alone. The episode reveals an important truth about international agreements: a treaty is only as strong as the willingness of outside powers to respect it, a lesson that would repeat again and again throughout the history of European colonization.

Adapted from Studio Aletheia's World Builders Academy curriculum library, drawing on classical world history resources on the Treaty of Tordesillas and European territorial claims.