Between 1452 and 1455, Pope Nicolas V issued a series of papal bulls authorizing the Portuguese to take African slaves. At first slave traders raided coastal areas and carried black people off. But the mines and fields of the colonies needed more and more slaves. In the early 16th century Spain began to issue licenses and contracts to supply slaves. By the 1750s large slaving companies were established. Most of Europe at the time was involved in the slave trade.