<P> The Treaty of Tordesillas was intended to solve the dispute that had been created following the return of Christopher Columbus and his crew, who had sailed for the Crown of Castile . On his way back to Spain he first reached Lisbon, in Portugal . There he asked for another meeting with King John II to show him the newly discovered lands . </P> <P> After learning of the Castilian - sponsored voyage, the Portuguese King sent a threatening letter to the Catholic Monarchs stating that by the Treaty of Alcáçovas signed in 1479 and confirmed in 1481 with the papal bull Æterni regis, that granted all lands south of the Canary Islands to Portugal, all of the lands discovered by Columbus belonged, in fact, to Portugal . Also, the Portuguese King stated that he was already making arrangements for a fleet (an armada led by Francisco de Almeida) to depart shortly and take possession of the new lands . After reading the letter the Catholic Monarchs knew they did not have any military power in the Atlantic to match the Portuguese, so they pursued a diplomatic way out . On 4 May 1493 Pope Alexander VI (Rodrigo Borgia), an Aragonese from Valencia by birth, decreed in the bull Inter caetera that all lands west and south of a pole - to - pole line 100 leagues west and south of any of the islands of the Azores or the Cape Verde Islands should belong to Castile, although territory under Catholic rule as of Christmas 1492 would remain untouched . The bull did not mention Portugal or its lands, so Portugal could not claim newly discovered lands even if they were east of the line . Another bull, Dudum siquidem, entitled Extension of the Apostolic Grant and Donation of the Indies and dated 25 September 1493, gave all mainlands and islands, "at one time or even still belonging to India" to Spain, even if east of the line . </P> <P> The Portuguese King John II was not pleased with that arrangement, feeling that it gave him far too little land--it prevented him from possessing India, his near term goal . By 1493 Portuguese explorers had reached the southern tip of Africa, the Cape of Good Hope . The Portuguese were unlikely to go to war over the islands encountered by Columbus, but the explicit mention of India was a major issue . As the Pope had not made changes, the Portuguese king opened direct negotiations with the Catholic Monarchs, King Ferdinand and Queen Isabella, to move the line to the west and allow him to claim newly discovered lands east of the line . In the bargain, John accepted Inter caetera as the starting point of discussion with Ferdinand and Isabella, but had the boundary line moved 270 leagues west, protecting the Portuguese route down the coast of Africa and giving the Portuguese rights to lands that now constitute the Eastern quarter of Brazil . As one scholar assessed the results, "both sides must have known that so vague a boundary could not be accurately fixed, and each thought that the other was deceived, (concluding that it was a) diplomatic triumph for Portugal, confirming to the Portuguese not only the true route to India, but most of the South Atlantic". </P> <P> The treaty effectively countered the bulls of Alexander VI but was subsequently sanctioned by Pope Julius II by means of the bull Ea quae pro bono pacis of 24 January 1506 . Even though the treaty was negotiated without consulting the Pope, a few sources call the resulting line the "Papal Line of Demarcation". </P>

As a result of a 1493 decree by the pope portugal acquired which modern-day south american country