Dividing the Ocean Sea

As the fifteenth century drew to a close, disputes between Spain and Portugal over territorial ownership of island archipelagos in the Atlantic were resolved by the Treaty of Alcáçovas in 1479-80. In this treaty, each of the Atlantic archipelagos was assigned between the two Iberian powers. This division of lands was acceptable to all parties until Christopher Columbus returned from his epic voyage of 1492-93, and with it the belief that he had reached “the islands of India beyond the Ganges.” Ownership of these newly discovered lands in the East Indies was claimed by Spain. King John of Portugal disputed this, exclaiming that these discoveries properly belonged to Portugal, as implied by the treaty of Alcáçovas.

To resolve their differences, in 1494 these two great Iberian powers, with the aid of the Vatican (itself a world power), composed the Treaty of Tordesillas, wherein they divided the entire Ocean Sea (as the Atlantic was then called) into two sovereign zones with a line that extended north and south from the Arctic Pole to the Antarctic Pole. The problem of ownership of lands might have been resolved had it not been for subsequent expeditions that pushed the boundaries of the unknown to a new and distant horizon. The voyage of Vasco da Gama in 1497-98, led the way to the Malabar coast of India by a southeast passage, thus opening a new sea route to the East Indies for Portugal. While the voyage of Magellan in 1519-22, reached the Orient by a southwest passage around the tip of South America. Each nation, keeping within its proscribed limits, had arrived at the same place on the opposite side of the world.

Both powers laid claim to the Moluccas (the Spice Islands) and the enormous wealth to be gained from them. When the Treaty of Tordesillas--a deceptively simple and straight forward treaty--was drawn up it was never explicitly stated, or even implied, that this line extended a full 360 degrees of the Earth’s circumference, and thus had a counter-meridian at the other side of the world .

“Dividing the Ocean Sea” takes the reader through the subsequent decades of negotiations and further treaties to determine ownership of new islands, in a new ocean.