It is considered the first international treaty of modern times. In addition to the Portuguese political representatives (Ruy de Sousa, Juan de Sousa and Arias de Almadana) and Castile (Enrique Enréquez de Guzmén, Gutierre de Cérdenas and Francisco Maldonado), two teams of geographers and experts participated in the negotiations to provide technical assistance to diplomatic decision-making. The Treaty of Tordesillas was invoked by Chile in the 20th century to defend the principle of an Antarctic area that extends along a meridian to the South Pole, and the assertion that the treaty made all Spanish (or Portuguese) lands a pole to the south.  The goods, sanctioned by the treaty, continued, even when Spain and Portugal were united as one king between 1580 and 1640, until the Treaty of Madrid was replaced by the Treaty of Madrid of 1750. The treaty effectively countered the bulls of Alexander VI, but was later sanctioned by Pope Julius II with the bull Ea quae pro bono pacis of January 24, 1506.  Although the treaty was negotiated without consultation with the Pope, some sources call the resulting line the “Pontifical Line of demarcation.”  Treaties are agreements between and between nations. Treaties have been used to end wars, settle land disputes and even destabilize new countries. The Treaty of Tordesillas of 7 June 1494 included agreements between King Ferdinand II of Aragon and Queen Isabella I of Castile and King John II of Portugal, which established a new dividing line between the two crowns, which ran from pole to pole, 370 leagues west of the Cape Verde Islands. The treaty was finally signed after complicated diplomatic negotiations between ambassadors and lawyers from both kingdoms. The change of a demarcation line separating the world between Spain and Portugal led to the birth of Brazil, as its eastern end fell within the Portuguese zone. This document is essential if we are to understand American history and the economic and cultural relations between Europe and America. This is why the treaty has become an important link not only with the history of the Atlantic Ocean, but also with the memory of the world that brought continents and civilizations separated by unknown oceans. In fact, the Europeans saw very little of the newly divided territory, since it was divided only by the treaty.
Castile gained land, including most of the Americas, which had little proven wealth in 1494. The easternmost part of Brazil today was Portugal, when Pedro Alvarez Cabral landed in 1500 on his way to India. Some historians claim that the Portuguese were already aware of the South American curvature, which represents most of Brazil before that time, so that its landing in Brazil was not an accident.  A scholar refers to Cabral`s landing on the Brazilian coast 12 degrees further south than the expected Cap Sao Roque, so that “the probability that such a land case was due to freak weather or navigational errors was low; and it is very likely that Cabral was ordered to investigate a coast whose existence was not only suspected, but already known.  The treaty established an imaginary length, from the North Pole to the south, passing 370 leagues west of the Cape Verde Islands (46o 37` of western length). But an agreement on how to identify the exact meridian, for which precise identification of longitude was essential, was not defined in the treaty. Portugal would have control over the eastern part and Castile on the west side. The treaty included rights to territories that were already to be discovered or discovered, but limited to those that did not yet have a Christian government.