On June 18, 1452, Pope Nicholas V, issues a statement (called a “papal bull”) called the Dum Diversas.
The Dum Diversas gives King Alfonso V of Portugal permission to reduce any “nonbelievers” to perpetual slavery.
The Portuguese take this and run, and begin enslaving West Africans, which gets beyond ugly very quickly.
On January 5, 1455, Pope Nicholas V issues the bull Romanus Pontifex, which further encourages the enslavement of African people and non-Christian natives in the New World.
This is just the beginning. Again, we’ll fast forward a few popes to Pope Alexander VI, who issues the Inter Caetera, also known as the Doctrine of Discovery.