The benefits of the African slave trade, such as they were, redounded entirely to those Western countries involved in it. They grew incredibly wealthy from slavery, amassing considerable sums from the buying and selling of human cargo. The wealth accrued from slavery gave European countries a firm incentive to continue their explorations of Africa, which they called the Dark Continent. In turn, this enabled the establishment of substantial colonies, which led to a sharp increase in the numbers of indigenous Africans being sold into slavery.

Not for the fist time in human history, and nor for the last, economic power led directly to political power. The global dimensions of the slave trade encouraged European powers to broaden their horizons and seek opportunities to expand their territories abroad. This they did with increasingly ruthlessness and lack of restraint, carving large empires out of the African continent that would increasingly form the basis of their economic and political power.

It is almost universally accepted that the slave trade was horrific. Millions of Africans were shipped across the Atlantic for lives of bondage in the New World. In fact, the trauma that was inflicted on its victims still lingers, and slavery reparations are being considered by some American leaders.

Since they were viewed as nothing more than a commodity, African slaves were part of the "triangular" trade between the New World, Europe, and Africa. That trade flourished for about two hundred years. The "commodity" was used as a labor force in the Americas. The Spanish had tried to use Indians as laborers, but their mortality rate was too high. The English had relied on indentured servants, but that became impractical after a while. Therefore, slaves imported from Africa became important laborers, particularly in agricultural areas such as the antebellum South and the West Indies.

Finally, by the early nineteenth century, there was substantial opposition to slavery in both Britain and the antebellum North.

The benefits of the African slave trade did not extend to millions of men, women, and children caught up in it. For them, the slave trade destroyed their families and condemned most of them to a life filled with horrors and indignities that are difficult for most in the modern Western world to imagine. 

One group of beneficiaries were the monarchs and merchants within the West African kingdoms who gained wealth and prestige by participating in the trade. For them, the trade brought manufactured goods, especially guns, that added to their power, and incentivized them to participate in the trade. Over time, however, European merchants, backed by the power of their nation-states, would increasingly dominate the trade.

Also benefiting from the trade were European slave merchants who bought slaves in Africa and sold them in American markets. While different European kingdoms dominated the trade from the sixteenth to the nineteenth centuries, these merchants, many of whom enjoyed royal monopolies on the trade, profited handsomely from the sale of people. Much of the money also flowed to the financiers that provided capital for the trade, including banking houses in almost every European kingdom.

Finally, there were European people in the colonies who profited from the labor of the people ensnared in the trade. They worked to produce cash crops (especially sugar), precious metals, and other commodities that fueled the Atlantic economy. Many of these planters, notably in the West Indies, became extravagantly wealthy. 

So the slave trade was immensely profitable for many of its participants. It was fundamental to the integration of the Atlantic economy in the colonial period. But all of this wealth was ultimately based on the kidnapping and sale of human beings.