Treaty of Zaragoza (1529): Settling the Moluccas Dispute

The Treaty of Zaragoza (also spelled Saragossa) was signed on 22 April 1529 by Emperor Charles V, as king of Castile and Aragon, and King John III of Portugal. It ended a bitter dispute over the Moluccas, the Spice Islands of eastern Indonesia, by having Spain sell its claim to Portugal and by fixing a dividing line on the far side of the world. It completed the division of the globe begun by the Treaty of Tordesillas.

Background: a line with no other side

In the Treaty of Tordesillas of 1494, Spain and Portugal agreed to divide newly discovered lands along a meridian 370 leagues west of the Cape Verde Islands. Portugal took everything to the east, Spain everything to the west. But the treaty did not define where the matching line, the antimeridian, ran on the other side of the Earth.

That gap mattered once the Portuguese reached the Moluccas around 1512. These small islands, especially Ternate and Tidore, were the world’s only source of cloves, and nearby islands supplied nutmeg and mace. Spices were among the most valuable goods in European trade, so the question of who owned them was worth fighting over.

The race to the Spice Islands

The Magellan-Elcano expedition, sailing west for Spain, reached Tidore in November 1521. Its leaders argued that the islands lay in the Spanish half of the world. Portugal disagreed. With no accurate way to measure longitude at sea, neither side could prove its case.

A joint commission of experts met at Badajoz and Elvas in 1524 but reached no agreement. Spain sent new fleets: García Jofre de Loaísa’s expedition left in 1525, and Álvaro de Saavedra sailed from Mexico in 1527. Spanish and Portuguese soldiers fought skirmishes in the Moluccas, each allied with rival local sultans.

The terms of the treaty

By 1529 Charles V needed money for his wars in Europe, especially against France, and had little hope of holding the distant islands. He was also John III’s brother-in-law, having married Isabella of Portugal in 1526. A sale offered a way out.

Under the treaty:

• Spain gave up its claim to the Moluccas in return for 350,000 ducats paid by Portugal.
• A line was drawn 297.5 leagues (about 17 degrees) east of the Moluccas. Lands west of it went to Portugal, lands east to Spain.
• Spain kept the right to reopen the question if it repaid the full sum, a clause that was never used.

John III ratified the agreement in 1530, and the Spanish expedition still in the islands eventually surrendered to the Portuguese.

The longitude problem

The heart of the dispute was scientific as much as political. Sixteenth-century navigators could measure latitude fairly well from the height of the sun or stars, but they had no reliable way to measure longitude, the east-west position, at sea. That required accurate timekeeping, which was not possible until marine chronometers were developed in the 18th century.

Each side therefore produced maps and calculations that placed the Moluccas on its own side of the line. Modern measurements show that the islands did in fact lie within the Portuguese half defined by Tordesillas, but no one in 1529 could prove it. The treaty sidestepped the question by turning a scientific argument into a commercial sale.

Key people

• Charles V (1500-1558): Holy Roman Emperor and king of Spain, who needed cash for his European wars and agreed to sell the Spanish claim.
• John III of Portugal (1502-1557): king from 1521, whose government paid the 350,000 ducats to secure the spice trade.
• Ferdinand Magellan and Juan Sebastián Elcano: leaders of the expedition whose arrival in the Moluccas in 1521 started the dispute.
• Diogo Ribeiro: a Portuguese cartographer working for Spain, whose world maps of the 1520s reflected the Spanish position on the islands.

Consequences

Portugal secured the clove trade for several decades, until local resistance and, from around 1600, Dutch competition weakened its hold. The Sultanate of Ternate expelled the Portuguese in 1575, a reminder that the treaty mattered more to European rivals than to the islands’ own rulers.

The Philippines lay west of the Zaragoza line and thus, on paper, in Portugal’s zone. Spain colonised them anyway after Miguel López de Legazpi arrived in 1565, arguing that the 1529 sale concerned only the Moluccas. Between 1580 and 1640, when the Spanish and Portuguese crowns were united under one king, the dispute largely lost its force.

Timeline

• 1494, 7 June: Treaty of Tordesillas divides the Atlantic world but leaves the antimeridian undefined.
• c. 1512: Portuguese ships reach the Moluccas.
• 1521, November: The Magellan-Elcano expedition reaches Tidore.
• 1524: The Badajoz-Elvas conference fails to settle the dispute.
• 1525: Loaísa’s fleet sails from Spain for the Moluccas.
• 1529, 22 April: Treaty of Zaragoza signed.
• 1530: Portugal ratifies the treaty.
• 1565: Spain begins colonising the Philippines, west of the line.

Why it matters

The Treaty of Zaragoza shows how two European crowns tried to divide the whole world between them with lines drawn on imperfect maps. It also shows how money and European politics, rather than geography, decided the fate of distant islands. Its line in the Pacific completed the Tordesillas division and shaped the colonial map of Southeast Asia.