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Why Was the Treaty of Tordesillas Impossible to Enforce? - The Treaty of Tordesillas and the Unenforceable Atlantic Line | Sleepy Facts About History · Sleepy Facts About History

0:04
Welcome to Sleepy Facts About History. In the
0:12
spring of 1493, Christopher Columbus returned
0:16
from a voyage he believed had reached Asia, inadvertently
0:19
triggering a diplomatic crisis between Portugal
0:22
and Castile. King John II of Portugal argued
0:27
the new lands fell within his established Atlantic
0:30
rights. bringing the two Iberian crowns to the
0:33
brink of war. To resolve this tension, negotiators
0:37
met in 1494 at the town of Tortosias, where they
0:42
drew a line 370 leagues west at the Cape Verde
0:45
Islands, allocating zones of expansion to the
0:49
west and east. This episode examines the Treaty
0:53
of Tortosias not as a grand vision of dividing
0:56
the globe, But as a fragile legal fiction built
0:59
on profound geographical uncertainty, we explore
1:03
why the line was practically unworkable, from
1:06
the lack of standardized maritime measurements
1:08
to the unsolved problem of calculating longitude.
1:12
We also look at how this bilateral agreement
1:15
ignored the sovereignty of indigenous peoples
1:18
and failed to bind other rising European powers.
1:22
I kept returning to one question while working
1:25
on this episode. How do you enforce a boundary
1:28
that exists only on an inaccurate chart? It is
1:32
fascinating to see how political pressure forced
1:35
diplomats to create a precise mark on parchment
1:38
that no ship could actually locate in the water.
1:41
The treaty is a striking example of how legal
1:45
claims and physical reality can entirely diverge.
1:51
In the spring of 1493, a navigator who did not
1:55
know where he had been met, a king who intended
1:58
to claim it anyway, the document they produced
2:02
together would divide the Atlantic with a line
2:04
that no ship could find and no compass could
2:07
hold. In the spring of 1493, Christopher Columbus
2:12
returned to Lisbon. He had sailed west under
2:16
the flag of Castile, and he brought news of lands
2:20
across the Atlantic. He insisted that these lands
2:24
were the outskirts of Asia. But his first stop
2:27
was not his sponsor's court. It was Portugal.
2:31
And there, in a meeting with King John II, the
2:35
trouble began. John II listened to Columbus's
2:39
account. Then he made a claim that threatened
2:42
to unravel everything. Those lands, he said,
2:46
fell within Portuguese rights. The Portuguese
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crown had spent decades exploring the Atlantic
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and the coast of Africa. A treaty signed in 1479
2:57
at Alcaçovas had recognized Portuguese claims
3:01
south of the Canary Islands. John II now argued
3:05
that Columbus's discoveries lay within that zone.
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He threatened to send a fleet to claim them.
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This was a crisis that produced the Treaty of
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Tordesillas. It was not a grand vision of dividing
3:18
the world. It was a specific diplomatic emergency.
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Two Iberian crowns stood on the brink of conflict
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over places neither fully understood, reached
3:31
by a navigator who had miscalculated where he
3:34
was. The question was not how to apportion the
3:37
globe. It was how to keep two small kingdoms
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from going to war over claims they could barely
3:44
substantiate. Columbus' error was not incidental.
3:49
He had sailed with a model of the Earth that
3:52
made it smaller than it is. He had convinced
3:55
himself that the lands he reached were part of
3:58
Asia. This meant he could not accurately say
4:02
where his discoveries lay relative to Portuguese
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zones of influence. The uncertainty was geographical
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as well as political. The treaty would be built
4:12
from its first words. on a navigator's mistaken
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confidence and a geography that no european yet
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comprehended to understand why this mattered
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we need to step back briefly by the late 15th
4:27
century portugal had spent nearly a century building
4:30
a system of atlantic exploration portuguese navigators
4:34
had pushed down the west coast of africa they
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had established trading posts gathered geographical
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knowledge and secured from the papacy a series
4:44
of bulls that granted exclusive rights to explore
4:47
and trade in those regions. The most important
4:50
of these, Romanus Pontifex in 1455, had given
4:54
the Portuguese crown broad authority along the
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African coast and across to India. The Treaty
5:01
of Alcácer Vaz in 1479, which ended a war between
5:05
Castile and Portugal, had confirmed Portuguese
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primacy in the Atlantic south of the Canaries.
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Castile retained the Canary Islands themselves.
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Columbus's voyage disrupted this arrangement.
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He had sailed for Castile, not Portugal. He had
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gone west, not south, and he had found, or so
5:28
he believed, a new route to the Indies that bypassed
5:31
Portuguese claims entirely. But geography is
5:35
not settled by belief. The lands Columbus reached
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were not where he thought they were, and their
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location relative to the Alcarfus line was genuinely
5:45
uncertain. Ferdinand and Isabella, the Catholic
5:49
monarchs of Castile and Aragon, understood that
5:52
Portuguese recognition of their claims would
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be essential. They turned to Pope Alexander VI,
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Rodrigo Borgia, a Valencian with long ties to
6:02
the Aragonese crown. In 1493, Alexander issued
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a series of bulls. These included Intecatsara,
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Eximiae Devotionis, and Dudum Siquidem. They
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granted Castile rights to lands west and south
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of a line drawn 100 leagues west of the Azores
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and Cape Verde Islands. The language was sweeping.
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The grants were enormous. And from Portugal's
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perspective, they were intolerable. John II rejected
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the papal line. He threatened war. The bulls
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had not solved the crisis. They had intensified
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it. Portugal's objection was not merely to the
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line's location. It was to the underlying assertion
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that the Pope could grant Castile exclusive rights
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to territories that Portugal considered within
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its own sphere of influence. The papacy was a
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useful source of legitimacy. But it was not a
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neutral arbiter that both sides would accept
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without question. What happened next is the heart
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of the story. Rather than fight, the two crowns
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negotiated directly. In 1494, representatives
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of Castile and Portugal met at Tordesilla, a
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town in Castile on the Douro River. They produced
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an agreement that modified the papal framework.
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The line was moved from 100 leagues to 370 leagues
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west of the Cape Verde Islands. Everything west
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of the line went to Castile. Everything east
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went to Portugal. Both crowns ratified the treaty.
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This is the moment that requires careful attention,
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because it is easy to misunderstand what was
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actually agreed. The treaty did not divide the
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world. It divided zones of expansion between
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two monarchies. It did not grant sovereign possession
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of anything. It allocated rights to explore,
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to trade, and to claim. And it was built on a
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series of imprecisions that made its central
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mechanism, the line itself, practically unworkable.
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Picture the scene at Tortesias. Negotiators from
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both crowns gather around a table. Before them
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lies a chart of the Atlantic, drawn from the
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accumulated knowledge of Portuguese and Spanish
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pilots. That knowledge was extensive in some
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regions, and nearly blank in others. With ink
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or a stylus, someone draws a vertical line through
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the ocean. The mark is precise on the parchment.
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But the men in that room know, even as they make
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it, that the mark corresponds to no visible feature
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on the water. There is no island, no reef, no
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change in current to announce where the line
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falls. It exists only on the chart, and the chart
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itself is wrong in ways they cannot fully measure.
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Consider what the treaty did not specify. It
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did not say which Cape Verde island served as
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the starting point for measuring the 370 leagues.
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The archipelago contains multiple islands. and
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their relative positions were known well enough
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to matter. Depending on which island a navigator
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chose, the line's location in the Atlantic could
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shift by a distance significant enough to affect
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claims to the South American coast. The treaty
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did not define the length of a league with precision.
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Different regions used different standards, and
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maritime measurement was inherently approximate.
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Most importantly, it provided no mechanism for
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locating the line at sea a mariner sailing across
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the atlantic in 1494 navigated by dead reckoning
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he estimated his ship's speed by watching the
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water pass the hull or by throwing a log overboard
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and timing its drift he estimated direction by
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compass the compass itself deviated from true
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north by an amount he could only guess each day
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each watch Each change of course added error.
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Over weeks at sea, the accumulated uncertainty
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could place a ship dozens or hundreds of leagues
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from where its pilot believed it to be. Latitude,
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the north -south position, could be measured
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with reasonable accuracy by observing the height
10:40
of the pole star or the sun at noon. But longitude,
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the east -west position, remained a notorious
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problem. No reliable method existed in 1494.
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This would remain unsolved for nearly three centuries.
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The negotiators at Tortosillas were drawing a
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line on a map that was itself inaccurate. They
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were using a measurement that was not standardized,
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from a starting point that was not specified,
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to create a boundary that could not be located
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by the people who were supposed to observe it.
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They were not ignorant of these problems. They
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were doing the best they could with the tools
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they had, under political pressure to produce
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an agreement. The result was a legal fiction
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of remarkable ambition and remarkable fragility.
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The practical consequences of this fragility
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became apparent almost immediately. Nowhere was
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this clearer than in the question of Brazil.
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In 1500, Pedro Alvarez Cabral, sailing for Portugal,
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made landfall on the eastern coast of South America.
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His fleet had been bound for India following
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the Portuguese route around Africa when winds
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and currents carried it westward across the Atlantic.
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The ships arrived off an unknown coast. Men went
12:02
ashore. They planted a marker, perhaps a cross,
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and declared the land for the Portuguese crown.
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The Portuguese claimed this territory. under
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the Treaty of Tordesillas, but did the line actually
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place Brazil within Portugal's zone? This is
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one of the most debated questions in the scholarship
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of this period. It is important not to overstate
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what we know. Some historians have argued that
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Portuguese navigators already had knowledge of
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the South American coast before 1500. They suggest
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that the 370 -league line was chosen precisely
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to include that coast within Portugal's sphere.
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Others contend that the line's placement was
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a diplomatic compromise without precise geographical
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intent. They argue that the Portuguese claim
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to Brazil was a retrospective justification rather
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than a fulfillment of the treaty's terms. The
13:00
evidence is incomplete and contested. What we
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can say with confidence is that the treaty's
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language was invoked to legitimize the Portuguese
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presence. But the actual location of the line
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relative to the South American coast was uncertain
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then, and remains uncertain now. The broader
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point is more important than any particular answer.
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The treaty created a framework for claims, not
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a geographical fact. When Cabral's men planted
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their marker on Brazilian soil, they were not
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confirming the accuracy of a line. They were
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extending a legal fiction into physical space.
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They were using the treaty's authority to justify
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an action that the treaty itself could not precisely
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authorize. The Tupi -speaking peoples who inhabited
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that coast had their own political arrangements,
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their own systems of authority and territory.
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They had not consented to the treaty. They had
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not been asked. The line on the Portuguese chart
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meant nothing to them, and they have no reason
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to recognize it. This gap between legal claim
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and geographical reality only widened as European
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exploration continued. The Treaty of Tordesillas
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had addressed the Atlantic. It said nothing about
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the other side of the globe. But both Castile
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and Portugal were moving toward Asia. The question
14:29
of where the line fell in the Pacific became
14:31
unavoidable. The Moluccas, the spice islands,
14:35
became the flashpoint. These islands were the
14:39
world's only source of cloves, nutmeg, and mace.
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Europeans used these spices to preserve meat,
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to flavor food, and to treat ailments ranging
14:50
from digestive trouble to the plague. Their rarity
14:53
made them extraordinarily valuable. They were
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worth more than their weight in gold in European
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markets. A single cargo of clothes could return
15:03
its investors many times over. Both crowns claimed
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the Moluccas. The problem was that no one could
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say with confidence which side of the antipodal
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line they fell on. The Magellan Expedition which
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sailed for Castile and completed the first circumnavigation
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between 1519 and 1522, intensified the dispute.
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Its survivors brought back geographical information
15:29
that complicated rather than resolved the question.
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The Spanish crown argued that the islands lay
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within its hemisphere. The Portuguese crown insisted
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they did not. The sultanates of the Moluccas,
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including Ternate and Tidore, conducted their
15:47
own diplomacy and warfare. They traded with whichever
15:51
Europeans arrived and maintained sovereignty
15:54
that neither Iberian crown acknowledged. In 1529,
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the two crowns attempted to settle the matter
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with a second agreement, the Treaty of Zaragoza.
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This treaty drew another line, this time in the
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Pacific. Portugal paid Castile 350 ,000 ducats
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for recognized rights to the Moluccas. The payment
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is a revealing detail. It suggests that the parties
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understood the antipodal line was even less locatable
16:26
than the Atlantic line. A financial transaction
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might substitute for geographical certainty.
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10 ,000 ducats was an enormous sum. It was a
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concrete measure of how much the legal fiction
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was worth to both parties. But the Zaragoza Line
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was no more enforceable than its predecessor.
16:47
It managed the dispute between the two Iberian
16:50
crowns without resolving the underlying problem.
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They were allocating territories they did not
16:56
control, using lines they could not locate, in
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a world where other powers were increasingly
17:01
unwilling to accept their arrangements. For the
17:06
Treaty of Tordesillas was never more than a bilateral
17:08
agreement. It had no authority over the French,
17:12
the English, or the Dutch. Francis I of France
17:17
is reported to have asked to see the clause in
17:20
Adam's will that excluded France from the new
17:23
will. The remark, whether apocryphal or not,
17:26
captures the attitude of rival European powers.
17:30
After the Reformation, The rejection of papal
17:33
authority by Protestant states made the treaty's
17:36
religious foundation even less tenable. The Dutch,
17:40
in particular, would become a major force in
17:43
Asian trade. They ignored Iberian claims entirely
17:46
and established their own presence in the Moluccas.
17:49
More fundamentally, the treaty had no authority
17:53
over the peoples whose lands it purported to
17:56
distribute. Indigenous nations in the Americas.
18:00
African states along the Atlantic coast, Asian
18:04
rulers in the Moluccas and beyond. These were
18:07
not parties to the agreement. They had not consented
18:12
to it. They were not bound by it. The treaty
18:16
was a European legal fiction that operated within
18:19
a European diplomatic sphere. Its extension to
18:23
the wider world was an assertion of power, not
18:26
a recognition of existing sovereignty. This is
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the distinction that must be held clearly in
18:32
mind. The Treaty of Tordesillas allocated claims
18:36
between Castile and Portugal. It did not transfer
18:40
sovereign possession. The difference is not merely
18:44
technical. A claim is a statement of intention,
18:47
a declaration of right that requires subsequent
18:50
action to make it real. Sovereign possession
18:54
implies actual control, recognized authority,
18:58
and the capacity to enforce decisions. The treaty
19:01
created the first. It could not create the second.
19:06
The gap between time and possession was filled,
19:09
where it was filled at all by conquest, negotiation,
19:13
settlement, disease, and the complex interactions
19:15
of European and non -European societies. It was
19:20
not filled by the line drawn at Tordesillas.
19:23
The treaty's legacy is real, but specific. It
19:27
shaped the pattern of Iberian expansion in the
19:30
Atlantic. It influenced the linguistic boundary
19:34
that would eventually separate Portuguese -speaking
19:36
Brazil from Spanish -speaking territories to
19:39
the west. It provided a vocabulary of legal justification
19:43
that European powers would use in various forms
19:46
for centuries. And its imprecision continued
19:50
to create diplomatic problems long after 1494.
19:55
When Portugal and Spain late negotiated the boundaries
19:58
of their South American territories, as they
20:01
did in the Treaty of Madrid in 1750, they still
20:05
had to reckon with the Tordesillas Line's ambiguity.
20:08
The line that could not be located in 1494 remained
20:13
a practical problem for negotiators three centuries
20:16
later. But the treaty did not divide the world.
20:20
It did not prevent conflict between Castile and
20:23
Portugal. Though it may have limited its scale,
20:27
it did not bind other European powers. It did
20:31
not acknowledge, let alone secure, the sovereignty
20:34
of indigenous peoples. When we look at modern
20:37
maps of South America and see the large Portuguese
20:41
-speaking country on the eastern coast, it is
20:44
tempting to see the Treaty of Tordesillas as
20:47
a successful prediction. But this is the wrong
20:50
way to understand the relationship. Brazil exists
20:53
as a Portuguese -speaking nation because of complex
20:56
historical processes that extended far beyond
20:59
the treaty. These processes included patterns
21:02
of settlement, the development of plantation
21:04
agriculture, the importation of enslaved Africans,
21:08
the interactions of European colonists with indigenous
21:12
populations, and the eventual political independence
21:15
of the colony. The treaty provided a legal framework
21:19
within which some of these processes operated,
21:22
but it did not determine them. The line was a
21:26
justification, not a cause. The same is true
21:30
of the treaty's failures. The geographical uncertainty
21:34
that made the line unlockatable was not a minor
21:38
technical difficulty. It was constitutive of
21:41
the treaty's nature as a legal fiction. The negotiators
21:45
and torturers were not incompetent cartographers.
21:48
They were participants in a political system
21:51
that used papal authority, diplomatic negotiation,
21:55
and cartographic representation to manage competition
21:58
between European powers. The line's imprecision
22:02
was not an accident to be corrected. It was a
22:06
feature of a particular way of organizing knowledge
22:09
and power. What remains uncertain. even after
22:13
centuries of scholarship is the precise intention
22:16
behind the treaty specific terms did the portuguese
22:20
negotiators know of the south american coast
22:23
when they agreed to the 370 league line did they
22:27
intend to include brazil within their sphere
22:30
the evidence is fragmentary and contested some
22:35
documents suggest portuguese knowledge of western
22:38
atlantic lands before 1500 Others are ambiguous
22:43
or silent. The question may never be fully resolved.
22:47
It is important not to present any answer as
22:50
established fact. Similarly, the exact location
22:54
of the line in modern coordinates remains disputed.
22:58
Depending on which Cape Verde island is used
23:01
as the starting point and which standard of the
23:03
league is applied, estimates vary significantly.
23:06
This uncertainty is not a failure of modern scholarship.
23:11
It is a consequence of the treaty's own imprecision,
23:14
built into the document from its origin. The
23:18
Treaty of Tordesillas was, in the end, a powerful
23:21
Iberian legal fiction. It was a shared legal
23:26
fiction between two crowns. It managed competition
23:29
between Castile and Portugal that might otherwise
23:33
have come to open conflict. It provided a framework
23:37
for claims that would shape the pattern of European
23:40
expansion in the Atlantic. It created a vocabulary
23:44
of justification that would echo through later
23:46
centuries. But its neat vertical line, so often
23:51
reproduced in textbooks as a clean division of
23:53
hemispheres, concealed a reality of geographical
23:56
ignorance, technical incapacity, and political
23:59
assertion. The line was imaginary. The geography
24:04
was unknown, and the peoples whose lands were
24:08
being allocated had no reason to recognize an
24:11
arrangement made by two monarchies in a Castilian
24:14
town they would never see. It was a line drawn
24:18
where no line could be drawn, dividing what no
24:21
one had surveyed, allocating what no one owned.