The 15th-century Portuguese exploration of the African coast is commonly regarded as the harbinger of European colonialism. In 1452, Pope Nicholas V issued the papal bull Dum Diversas, granting Afonso V of Portugal the right to reduce any "Saracens, pagans and any other unbelievers" to hereditary slavery which legitimized slave trade under Catholic beliefs of that time. This approval of slavery was reaffirmed and extended in his Romanus Pontifex bull of 1455. These papal bulls came to serve as a justification for the subsequent era of the slave trade and European colonialism, although for a short period as in 1462 Pius II declared slavery to be "a great crime". The followers of the church of England and Protestants did not use the papal bull as a justification. The position of the church was to condemn the slavery of Christians, but slavery was regarded as an old established and necessary institution which supplied Europe with the necessary workforce. In the 16th century, African slaves had replaced almost all other ethnicities and religious enslaved groups in Europe. Within the Portuguese territory of Brazil, and even beyond its original borders, the enslavement of Native Americans was carried out by the Bandeirantes.