Abolition of slavery and abolition of the slave trade, though often linked, followed rather different paths. Typically, the slave trade was abolished thirty to sixty years before slavery itself because of the understandable fact that the public objected to the conditions of slave ships, to premature death, and to the separation of families, before it became hostile to the rather more abstract issue of property in persons.

A second and more important distinction: the clear interaction between abolitionist activity and slave rebellions that helped bring about the end of slavery had no parallel in the ending of the slave trade. Slave traders continued to bring Africans into Saint-Domingue two years after the beginning of the only successful slave revolution in history. As for the captives on board slave vessels, resistance was a constant, always increasing the costs of slave traders (and thus reducing the numbers carried off from Africa), but there was no Middle Passage counterpart to the Haitian revolt, no on-board counterpart to the Jamaica rebellion of 1831, which hastened the 1833 legislation ending slavery in British territories.

For three centuries, Africans rebelled against the crews who confined them, but no increased incidence of rebellion can be observed during the long struggle to suppress the transatlantic traffic. Indeed, because of the increased, and as yet unexplained, incidence of children among captives after 1810, there were actually fewer shipboard revolts. 

National and International Campaigns

The ending of the slave trade came about in two stages in most countries. The first was a struggle to pass formal laws against human trafficking, and the second was the fight to make those laws effective in the face of the newly illegal traffic, which in most cases continued for several decades after it was outlawed. Unlike the struggle against slavery itself, which was fought within the confines of each state, there was always a strong international component in the campaign against the slave trade. Many nations took action only after signing treaties, and the issue became inextricably intertwined with the emergence of international law, the definition of piracy, and the thorny question of intervention by one sovereign state in the affairs of another, in the face of what today would be called human rights abuses.

The narrative of formal abolition of the slave trade is straightforward given that it was completed in less than four decades — a rather striking fact considering that long-distance slave trading had been an acceptable commerce very likely since before the first written records. Paradoxically, what proved to be the first move against the slave trade was actually a device to preserve the institution.

In 1787, as part of the accommodation between northern and southern states, the U.S. Constitution prohibited any federal interference with the international slave trade for twenty years. But the U.S. Congress interpreted the provision as a permit to intervene as soon as the twenty years were up. By then, individual states had prohibited their citizens from participating in the slave trade from Africa.

But the first national initiative was taken by the Danes, who in 1792 passed legislation decreeing the end of the African trade, to take effect in 1802. The United States federal government banned the traffic outright on March 2, 1807, but left sufficient loopholes so that, each year until about 1820, a few hundred enslaved Africans continued to arrive in the U.S. legally, apart from those smuggled in. Later in the same month the British, who had come close to abolishing their own very large traffic several times after 1787, followed suit, and thus, in just five years, nations that had controlled almost half the transatlantic slave trade declared the traffic illegal.

This was a false dawn. Whenever a branch of the slave trade was interdicted, even if the ban was effective, there was always the question of how quickly other nations would simply fill the resulting gap, thus leaving the volume of the trade unaffected. Getting all nations to agree to formal abolition took another quarter century. In 1814, a major slaving nation, Holland, decreed abolition of her traffic (though the last authentically Dutch slaver had probably sailed five years earlier).

The Portuguese undertook to give up their traffic north of the equator in a treaty with Britain the following year, though the charter outlawing it dates only from the beginning of 1818. But the much larger Portuguese southern Atlantic trade remained legal for another eighteen years. A French abolition law passed in April 1818, though it added nothing to the administrative instructions of 1815 to treat Africans arriving in French colonies as "smuggled goods", while the Spanish crown, again in response to a treaty with the British, promulgated a cedula that took effect in 1820 and incorporated the terms of the treaty.

This left Brazil, an independent nation since 1822 (but an inheritor of all Portuguese treaty obligations until that point), with a trade south of the equator that was still within the law in Portuguese, if not British, eyes. The first Brazilian measure banning the traffic passed in November 1831 — before the Portuguese themselves took action. With every one of these national measures (except for the Dutch case), there was, however, a gap, measured in decades, between the proscription and the effective enforcement of the law. At least 1.5 million Africans arrived in the Americas in violation of the various laws against the slave trade.

The Courts of Mixed Commission

This illegal inflow could be effectively interrupted at one of three stages: at the point of dispatch of the captives in Africa, during their transatlantic voyage, or after their arrival in the Americas. Action in the first and the third phases ultimately hinged on public attitudes in the countries either sending or receiving captives. No country in the nineteenth century had the power to invade recalcitrant states and enforce abolition, if indeed "freedom" can ever be imposed by force. Interruption of the second phase, the transatlantic voyage, was both a diplomatic and a naval issue.

Punitive action on the high seas against foreign nationals required, first, the assent of the nation to which the offender belonged and, second, sufficient forces to make the action possible. The slave trade was by definition an international activity, and laws were still very much evolving in the early nineteenth century. Several nations, including Britain and the U.S., declared slave trading to be piracy, an offence in international waters which in theory any nation could suppress. But to this day the international community has never succeeded in prosecuting slave traders for piracy. Even if it had, it was always rare for one nation to put citizens of another on trial for piracy, much less to execute them.

The largest sweep against piracy that the British navy ever carried out was along the coast of Africa in 1721-22. They detained over two hundred pirates, many of them French. Ninety-one were condemned, fifty-four of whom were hung in batches at British forts distributed along the Gold Coast. Every one of the foreign nationals was released.

It was no different in the nineteenth century. The British, Dutch, Spanish, Portuguese, and several other minor maritime powers eventually set up bilateral courts to adjudicate ships suspected of slave trading. These were called Courts of Mixed Commission and were located at different times in Sierra Leone; Luanda, Angola; Cape Town, South Africa; Rio de Janeiro, Brazil; Paramaribo, Suriname; Kingston, Jamaica; and New York.

Such courts could confiscate vessels, equipment, and merchandise, as well as release captives, but could exact no penalties against crews or owners. Given that slave traders could often repurchase these items (except for the captives) at the subsequent prize auction, these provisions were not a huge deterrent. France (except for a short period), Sardinia (with strong links to Bahia, Brazil), and, until 1862, the United States would not even go this far. Like all other nations, they were prepared to arrest and try their own nationals, but would allow foreign powers (usually, in practice, Britain) only to hand over any suspects for adjudication in their own domestic courts.

The 'Liberated Africans'

Possessing the largest navy in the world, the British had the military capacity to intercept and dispose of slave ships as they saw fit. In general terms, European powers could always command more force on the high seas than in foreign territory. But the diplomatic cost of unilateral action on the high seas would have been high, and if the modern traffic in illegal substances is any indication, it would not have stopped trafficking anyway. When the British did take such action, it was always against weaker powers, such as Brazil and Portugal, and rarely against the French or the United States.

The British role in suppression of the slave trade was large, even within these constraints, but from the perspective of human rights, somewhat ambivalent. By the mid-1840s, more than sixty British, French, American, and Portuguese warships were patrolling the African coast. But every anti-slave-trade treaty signed in the nineteenth century had Britain as one of the signatories. Of 6,921 voyages known to have been involved in the slave trade after 1807, 1,799 (about 22 percent) were interrupted when the ships were captured, and all but 233 of these detained ships were taken by the British navy. Many were empty and were condemned for carrying slave-trading equipment rather than slaves.

Nevertheless, 160,000 Africans were liberated from their holds as a result. Some of these "re-captives" — also called Liberated Africans — lived out their lives as peasants in villages in Sierra Leone, the Bahamas, and Trinidad. Others were removed to the British Caribbean as indentured servants after slavery was abolished there. Another group became low-wage municipal workers in Brazilian cities. The least fortunate were spirited away to Cuban sugar plantations and effectively remained slaves or, worse, were sold a second time after being kidnapped from the Sierra Leone village where they had been resettled. The great majority did escape this fate, however, and their personal details are recorded in huge registers of "Liberated Africans" in archives in Freetown, Rio de Janeiro, and London.

An "Illegal" Repression

But the fascinating fact is that many of the British actions were illegal. In conducting their campaign against the slave trade, the British frequently broke even the nascent dictates of early-nineteenth-century international law. During the Napoleonic Wars they assumed belligerent rights to stop and search the ships of all nations, and whenever they came across a slave trader, they further assumed that their own abolition law applied and thus confiscated vessel and captives alike. An extremely vague declaration against the slave trade in an 1810 treaty with Portugal was taken as a basis for capturing dozens of Portuguese slave ships, even though Portugal was a wartime ally. The British law officers themselves could make no sense of the clause, and heavy reparations were paid.

At the end of the war, the navy's belligerent rights came to an end, yet it continued to detain French and Spanish slave vessels quite illegally. When again the law officers disavowed such tactics, the government attempted to negotiate, first, a right of search and, second, an anti-slave-trade treaty with every other maritime nation. When the Brazilian and Portuguese governments refused to comply, or in one case to extend a treaty to which they had agreed, the British parliament passed legislation allowing the navy to try any slave vessels flying a Brazilian or Portuguese flag into English courts an unprecedented extension of British law to foreign nationals.

The British foreign secretary, Lord Palmerston, used secret service funds to bribe Brazilian politicians (including the negotiator of the anti-slave-trade treaty), subsidize Brazilian newspapers that would print anti-slave-trade material, and hire a network of spies around the Atlantic world. Finally, in 1850, Palmerston authorized the navy to invade Brazilian waters and destroy the property of slave traders, a clear casus belli.

Repression of the Slave Trade in Africa

The British also aggressively pursued treaties with African powers, beginning on the east coast with the sultan of Zanzibar in 1838. The provisions included not only the ending of the slave trade but also most-favored-nation status for British commerce, freedom of religion, and freedom to trade with any individual or group.

Not surprisingly, there were few takers despite promises of subventions. When rulers in the Galinhas (Guinea-Bissau) signed such a treaty in 1840 under the guns of a British fleet, it was subsequently repudiated, as were treaties in Cabinda and Ambriz (Angola) signed under similar circumstances. The British lowered their demands, and the first ratified treaty was in the Cameroons the following year.

By 1857 there were forty-five such treaties, but it was not until the 1860s that they covered all the major embarkation points of the Atlantic slave trade. Even the king of Dahomey entered such an agreement, although given the impotence of British land-based forces at the time, he was able to break it with little fear of retribution. Whydah and Abomey, the Dahomey capital, were both beyond the reach of the British navy.

In fact, on the African side of the Atlantic, British measures against the slave trade may be viewed as the precursor to European partition of the subcontinent later in the century. The enormous buildup of the British navy off the African coast triggered a competitive response from the French who, despite having no treaties in place that would allow them to search any vessel flying a non-French flag, matched the British, cruiser for cruiser, in the mid-1840s. These vessels had no impact whatsoever on suppression of the slave trade.

The French also increased their territorial presence in Senegal and other places on the West African coast as a counterweight to rising British influence. For their part, the British effectively founded their largest colony in Africa, Nigeria, in 1851 when they occupied Lagos and drove out the slave traders at the second attempt.

From the standpoint of international law, these assaults were not different from the attacks on Brazil in the previous year. In the illegal phase of the traffic, many centers of the slave trade shifted from offshore islands to secluded estuaries and inlets that were clearly within the jurisdiction of African states.

British naval officers did not always obtain African permission before launching these attacks. More fundamentally, the large European presence and the willingness of European navies to intervene in business disputes between African and European merchants tilted the commercial balance toward the European side for the first time in four centuries of commercial exchange in West Africa. Increasingly, where African polities had formerly provided the rule of law and the security that commercial exchange required, now it was provided by various European powers.

The Failure of Naval Action

Interestingly, none of these measures, except in part the assault in Brazil in 1850, was successful despite the fact that, by the mid-1840s, 10 percent of the British navy was deployed against the slave trade. Naval action, like slave revolts, raised the cost of doing business and therefore the prices of slaves in the Americas. Given a downward-sloping demand curve for enslaved labor, it thus reduced the number of Africans purchased and carried across the Atlantic.

Of course, because naval action increased risk for the slave traders, it also increased their profit rates. But naval action could not in itself halt the slave trade. Blockades have rarely been effective in history, and patrolling the sea off well-known ports of embarkation in Africa and disembarkation in the Americas did not spawn an exception to this tendency. So unsuccessful was the navy that, in Britain, a parliamentary campaign to withdraw the cruisers from anti-slave-trade duties came very close to success in the late 1840s.

The failure underscored a broader dilemma. Successful enforcement of human rights at the point of a gun is much rarer than many campaigners against abuses around the world are prepared to concede. In the past, slavery was destroyed by the application of force, but the attitudes that sustained slavery, as demonstrated by the case of the American South in the aftermath of the Civil War, are decidedly less susceptible to military action.

For the nineteenth-century slave trade, these general considerations imply that suppression could come about only when the regions that either dispatched captives across the Atlantic—phase one of the transatlantic movement of captives from Africa to the Americas—or the regions that received those captives—phase three—decided to take action.

The Suppression of the Slave Trade

African history is scattered with cases of societies that refused to sell captives into transatlantic slavery. But from a global perspective, African political and military power, as well as African slavery, was highly dispersed. Effective action would have required an unlikely degree of coordination. Such action was much more likely on the American side of the Atlantic.

Both large-scale slaveholdings and political power (Brazil, Cuba, the U.S., the British and French Caribbean) were heavily concentrated and therefore easier to control. And indeed, the key initiatives that ended the transatlantic slave trade came from regions in the Americas that had continued to allow slave imports after formal abolition. A shift in public opinion against the slave trade, accompanied by serious attempts to enforce the law, is clearly discernible in Brazil between 1831, when abolition was first proclaimed, and 1850, when the government began to take serious action against slave merchants, culminating in the expulsion of Portuguese citizens involved in the business.

In Cuba, the other major market for slaves in the mid-nineteenth century, a repressive regime meant that public opinion had much less impact, but in 1862 a new captain-general of the island began to expel slave traders and dismiss officials who had been bribed to permit new arrivals.

What holds true for suppression in the final era of the slave trade also applies to the disappearance of the trade in other regions of the Americas earlier in the century. When the authorities of the importing region became serious about ending the trade, then the trade ended. This happened in the British case in 1807 (except for a few thousand shipwrecked Africans over the next half century), the Dutch after the Napoleonic Wars, the French in 1831, and less certainly, given the arrival of several thousand African captives before 1820, and indeed two slave vessels from Africa in 1858 and 1860, the U.S. after 1807.

It should nevertheless be noted that while penalties against slave trading grew more severe over time — in the U.S. in 1820 and Britain in 1824, slave trading was declared a capital offence — few sentences resulted in extended imprisonment, and only one man was ever executed for slave trading. This was Nathaniel Gordon, in 1862, and Lincoln's refusal to commute his sentence had much to do with the outbreak of the Civil War.

Confiscation of property and fines were the normal outcome of successful prosecutions, though most decisions were taken in international courts of one kind or another, where penalties against persons have always been uncommon. It would seem that at no point did governments or the general public anywhere ever view slave trading as equivalent to murder.

Thus the key events in the suppression of the slave trade stem from changing attitudes rather than military intervention by the British. A half century of British diplomatic pressure and the intervention in Brazil in 1850 were not without significance, but a perspective that spans the last five centuries suggests a global shift in values: whereas slavery was once accepted and the slave trade viewed as a useful but unremarkable institution present in most societies, it became inconceivable that either chattel slavery or the slave trade could exist ever again.

In the last three centuries, such a shift has happened in one country after another so that today no state sanctions slavery or slave trading. In some countries, the change manifested itself as a popular campaign against abuse, while in others it happened with less fanfare. But in all instances the end result was the same. The fact that in our own day, the terms "modern slavery" and "modern slave trade" can increasingly be used to describe activities that no captive emerging from the hold of a nineteenth-century slave vessel would recognize as slavery is, in a sense, testament to how far and how fast values have altered.

David Eltis
Robert W. Woodruff Professor of History
Emory University


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