It was the Dutch, however, who launched the oversea slave trade as a regular institution.  They began their fight for freedom from Spain in 1579; in 1595, as a war measure against Spain, who at that time was dominating Portugal, they made their first voyage to Guinea.  By 1621 they had captured Portugal’s various slave forts on the west coast and they proceeded to open sixteen forts along the coast of the Gulf of Guinea.  Ships sailed from Holland to Africa, got slaves in exchange for their goods, carried the slaves to the West Indies or Brazil, and returned home laden with sugar.  In 1621 the private companies trading in the west were all merged into the Dutch West India Company, which sent in four years fifteen thousand four hundred and thirty Negroes to Brazil, carried on war with Spain, supplied even the English plantations, and gradually became the great slave carrier of the day.

The commercial supremacy of the Dutch early excited the envy and emulation of the English.  The Navigation Ordinance of 1651 was aimed at them, and two wars were necessary to wrest the slave trade from them and place it in the hands of the English.  The final terms of peace, among other things, surrendered New Netherlands to England and opened the way for England to become henceforth the world’s greatest slave trader.

The English trade began with Sir John Hawkins’ voyages in 1562 and later, in which “the Jesus, our chiefe shippe” played a leading part.  Desultory trade was kept up by the English until the middle of the seventeenth century, when English chartered slave-trading companies began to appear.  In 1662 the “Royal Adventurers,” including the king, the queen dowager, and the Duke of York, invested in the trade, and finally the Royal African Company, which became the world’s chief slave trader, was formed in 1672 and carried on a growing trade for a quarter of a century.  Jamaica had finally been captured and held by Oliver Cromwell in 1655 and formed a West Indian base for the trade in men.

The chief contract for trade in Negroes was the celebrated “Asiento” or agreement of the King of Spain to the importation of slaves into Spanish domains.  The Pope’s Bull or Demarkation, 1493, debarred Spain from African possessions, and compelled her to contract with other nations for slaves.  This contract was in the hands of the Portuguese in 1600; in 1640 the Dutch received it, and in 1701 the French.  The War of the Spanish Succession brought this monopoly to England.

This Asiento of 1713 was an agreement between England and Spain by which the latter granted the former a monopoly of the Spanish colonial slave trade for thirty years, and England engaged to supply the colonies within that time with at least one hundred and forty-four thousand slaves at the rate of forty-eight hundred per year.  The English counted this prize as the greatest result of the Treaty of Utrecht (1713), which ended the mighty struggle against the power of Louis XIV.  The English held the monopoly until the Treaty of Aix-la-Chapelle (1748), although they had to go to war over it in 1739.