Dias was never properly rewarded by his sovereign, and he became the forgotten man of Portugal’s Age of Discovery. He did supervise the building of ships for Vasco da Gama, but was not included in Gama’s climactic voyage to India. Only his death, in 1500 while playing an inconspicuous part in Cabral’s thirteen-ship fleet off the coast of Brazil, was appropriate. A hurricane sank four of Cabral’s ships, one of which was commanded by Dias, “casting them into the abyss of that great ocean sea… human bodies as food for the fish of those waters, which bodies we can believe were the first, since they were navigating in unknown regions.”

A quick follow-up to Dias’ discovery might have been expected. But the next step was delayed – by domestic problems in Portugal, by a disrupted succession to the crown, and especially by the running dispute that kept Portugal on the brink of war with Spain. Ironically, the discoveries of Columbus himself proved to be the principal cause of these troubles, which postponed for a full decade the sequel to Dias’ rounding of the Cape.

When King John II received word of Columbus’ discovery of new islands in the Atlantic, he announced, in March 1493, that these new lands, because of their proximity to the Azores and for other reasons, rightly belonged to Portugal. The ensuing disputes between King John of Portugal and King Ferdinand of Castile, and their rivalry for the support of the Pope, who presumably had the power to assign to Catholic kings the worldly governance of all newly discovered parts of the earth, resulted in the famous Treaty of Tordesillas (June 7, 1494). Spain and Portugal both acquiesced in a papal line which was to run north and south at 370 leagues (about 1,200 nautical miles) west of the Cape Verde Islands. Lands to the west of the line would belong to Spain, those eastward to Portugal. This agreement did evade war for the moment, and remains one of the most celebrated treaties in European history. But it was so full of ambiguities that nobody knows whether it really went into effect. From which Cape Verde island should the line be measured? Precisely how long was a league? And centuries would pass before the technology existed to draw the required precise line of longitude. In any event, in addition to securing Portugal’s claim to Brazil, whose existence then may or may not have been known, the treaty did affirm Portugal’s right to the eastward sea path to the Indies.

“The Portuguese Discoverers”, from “The Discoverers”, Daniel J. Boorstin, The National Board for the Celebration of Portuguese Discoveries, Lisbon, 1987