While Portuguese explorers sighted lands west of the Ocean Sea, Christians in the east worried about the Ottoman Turks. They were rapidly gobbling up the former Byzantine Empire and near taking possession of Constantinople. The Muslims had surrounded the capital city, but had not yet breached her three massive walls.

Reconstructed walls of Constantinople [now Istanbul].(1)

Slavery Made Hereditary

In 1452, Pope Nicholas V issued a bull known as Dum Diversas [literally Until Different, or Diverse] that commanded Christians everywhere to “attack, conquer, and subjugate Saracens [Muslims], pagans, and other enemies of Christ wherever they may be found.” For the Portuguese and Castilians, that also meant the Saracens to the south in Al-Andasus [Andalusia] on the Iberian Peninsula, and the pagans in Africa.

As part of “subjugating the Saracens and pagans,” Dum Diversas declared that Christians should, “reduce any Saracens, pagans, and any other unbelievers to perpetual slavery.” Perpetual slavery meant that once a person was a slave, his children were also slaves. The Pope had sanctioned slavery as a hereditary condition, which would be recognized in such places as the United States of America until their Civil War in the mid-1800s.

Ottoman Turks Captured Constantinople

The conflict worked both ways. The very next year, 1453, Mehmet(2)the Conqueror and his army of Ottoman Turks finally broke through the walls protecting Constantinople and claimed the city for Islam. From that time to today, the Muslim city has been called Istanbul. This was a huge setback for the Christian nations and for the House of Avis’ goal to eliminate infidels.

It was a huge boost for the Muslims, who gained control of the immensely important waterway known as the Bosporus Strait between the Black Sea and the Mediterranean. For all the northern countries, including Russia, the Black Sea provided the only access to waterways that did not freeze during winter.

Peri Reich, Constantinople, c1513-1528. South is at the top, with the Bosporus Strait on the left.(3)

The Muslims also brought with them a culture that was in many ways more interested in learning, more civilized, and more creative than many European cultures. They built beautiful architecture. And did you know they brought Arabian coffee and the croissant pastry with them to Europe? The croissant was the symbol of the Turkish flag. [When you enjoy your next cup of coffee, thank the Turks.]


  1. Constantinople’s Walls. By Bigdaddy1204 [GFDL ( or CC-BY-SA-3.0 via Wikimedia Commons. Image source:
  2. Mehmet is another form of Mohammad, or Muhammad.
  3. Reis, Peri Constantinople. Between c1513 and 1528. {{PD-old}} Public Domain. Image source: www

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