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.
From this agreement the slave traders reaped a harvest. The trade centered at Liverpool, and that city's commercial greatness was built largely on this foundation. In 1709 it sent out one slaver of thirty tons' burden; encouraged by Parliamentary subsidies which amounted to nearly half a million dollars between 1729 and 1750, the trade amounted to fifty-three ships in 1751; eighty-six in 1765, and at the beginning of the nineteenth century one hundred and eighty-five, which carried forty-nine thousand two hundred and thirteen slaves in one year.
The slave trade thus begun by the Portuguese, enlarged by the Dutch, and carried to its culmination by the English centered on the west coast near the seat of perhaps the oldest and most interesting culture of Africa. It came at a critical time. The culture of Yoruba, Benin, Mossiland, and Nupe had exhausted itself in a desperate attempt to stem the on-coming flood of Mohammedan culture. It has succeeded in maintaining its small, loosely federated city-states suited to trade, industry, and art. It had developed strong resistance toward the Sudan state builders toward the north, as in the case of the fighting Mossi; but behind this warlike resistance lay the peaceful city life which gave industrial ideas to Byzantium and shared something of Ethiopian and Mediterranean culture.
The first advent of the slave traders increased and encouraged native industry, as is evidenced by the bronze work of Benin; but soon this was pushed into the background, for it was not bronze metal but bronze flesh that Europe wanted. A new tyranny, blood-thirsty, cruel, and built on war, forced itself forward in the Niger delta. The powerful state of Dahomey arose early in the eighteenth century and became a devastating tyranny, reaching its highest power early in the nineteenth century. Ashanti, a similar kingdom, began its conquests in 1719 and grew with the slave trade. Thus state building in West Africa began to replace the city economy, but it was a state built on war and on war supported and encouraged largely for the sake of trade in human flesh. The native industries were changed and disorganized. Family ties and government were weakened. Far into the heart of Africa this devilish disintegration, coupled with Christian rum and Mohammedan raiding, penetrated. The face of Africa was turned south on these slave traders instead of northward toward the Mediterranean, where for two thousand years and more Europe and Africa had met in legitimate trade and mutual respect. The full significance of the battle of Tenkadibou, which overthrew the Askias, was now clear. Hereafter Africa for centuries was to appear before the world, not as the land of gold and ivory, of Mansa Musa and Meroe, but as a bound and captive slave, dumb and degraded.
The natural desire to avoid a painful subject has led historians to gloss over the details of the slave trade and leave the impression that it was a local west-coast phenomenon and confined to a few years. It was, on the contrary, continent wide and centuries long and an economic, social, and political catastrophe probably unparalleled in human history.
The exact proportions of the slave trade can be estimated only approximately. From 1680 to 1688 we know that the English African Company alone sent 249 ships to Africa, shipped there 60,783 Negro slaves, and after losing 14,387 on the middle passage, delivered 46,396 in America.