Danish slave trade occurred separately in two different periods. During the Viking Age, thralls (Norse slaves) were an important part of the economy and one of the main reasons for the raids on England where slaves were captured. This practice was abolished once Denmark became Christian. Trading black slaves was part of the transatlantic slave trade by Denmark-Norway around 1671, when the Danish West India Company was chartered, to 1802, when the Dano-Norwegian regent Prince Frederick carried out a ban on the country's participation in the trade. As of 1778, it was estimated that the Dano-Norwegians shipped about 3,000 Africans to the Danish West Indies annually to be sold as slaves. The country's ships transported approximately 100,000 enslaved Africans, about 2% of the total number the early 19th century.
Jensen, Niklas Thode; Simonsen, Gunvor. "Introduction: The historiography of slavery in the Danish-Norwegian West Indies, c. 1950-2016." Scandinavian Journal of History Sep-Dec2016, Vol. 41 Issue 4/5, p475-494.