Conquerors: How Portugal Forged the First Global Empire

by Roger Crowley

In 1479, to end an earlier war, the two monarchies had agreed to draw a horizontal frontier through the Atlantic Ocean, ratified by the pope, that defined areas of exclusive exploration. João believed that Columbus had discovered land within his domain and prepared to send his own expedition. The Spanish appealed to Alexander VI, the Spanish Borgia pope, who found in their favor, cutting Portugal out of huge swaths of the Atlantic Ocean that they believed they had carved out for themselves. Suddenly Portuguese Atlantic hegemony was threatened, and they were not about to have their decades of investment snatched away. João threatened war. The two sides agreed to face-to-face negotiations, bypassing the pope, to defuse a major diplomatic row. At the small and ancient town of Tordesillas, on the plains of central Spain, a delegation from each side met to bargain for the world. Here they simply cut the globe in two with a vertical line through the Atlantic Ocean “from the Arctic to the Antarctic pole”; to the east of this line was to be Portuguese; to the west, Spanish. João and his team of astronomers and mathematicians, probably more experienced and skillful, forced their opponents to have this line moved from its original position, proposed by the pope, more than a thousand miles to the west—midway