After learning of the Castilian-sponsored voyage, the Portuguese King sent a threatening letter to the Catholic Monarchs, King Ferdinand and Queen Isabella, stating that by the Treaty of Alcáçovas signed in 1479 and by the 1481 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. The Portuguese king also 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 1493 Pope Alexander VI (Rodrigo Borgia), an Aragonese from Valencia by birth, decreed in the bull "Inter caetera" that all lands west of a pole-to-pole line 100 leagues west of any of the islands of the Azores or the Cape Verde Islands should belong to Castile, although territory under Christian 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 1493, gave all mainlands and islands, "at one time or even still belonging to India" to Spain, even if east of the line.