@siegmund, indeed all europeans engaged in the slave trade.
When britain decided it was to be illegal though the royal navy was used to enforce it. Just done some research on it
____
As a first step, Britain outlawed slavery for its own flag vessels in 1807. As a consequence, during the Napoleonic Wars, slave ships from enemy states were captured. Slaves on these ships were set free, usually in Sierra Leone. By 1815, Britain, Russia, Austria, Prussia, France, the Netherlands, Sweden and the United States had agreed to prohibit the transatlantic slave trade.
In 1817, Spain also agreed to abolish the slave trade north of the equator and, in 1820, to abolish it completely. These were conventions that reflected the preferences of rulers in the signatory states. H owever, despite these commitments, the slave trade was so lucrative that large numbers of Africans continued to be transported across the Atlantic.
The major effort to enforce the ban on slaving was undertaken by Britain. Between 1818 and 1820, Britain signed treaties with a number of European countries that gave British warships the right to search and seize vessels suspected of engaging in the slave trade.
Brazil and Portugal were the most recalcitrant slave-trading countries. Brazilian agriculture was heavily dependent on slave labor. Immediately after abolishing the slave trade for British shipping in 1807, Britain began to put pressure on Portugal, whose colonies in Africa and South America were both a major source of and point of sale for slaves.
Portugal at first rejected British initiatives. However, when France invaded Portugal in late 1807, the Portuguese royal family was forced to flee to Brazil under British protection. In 1810, Portugal signed a commercial treaty with Britain that provided in part that Portugal would cooperate in gradually abolishing the slave trade.
Britain conceded to Portugal the right to continue slave trading within its African territories. In 1815, Portugal signed an agreement with Britain agreeing to stop slave trading north of the equator. This commitment, though, was only of limited consequence since most of Portugal's trade between Africa and Brazil was south of the equator.
In 1839, Britain unilaterally authorized its navy to board and seize suspected slavers that were flying the Portuguese flag. This came after long and unsuccessful efforts to sign a bilateral treaty with Portugal authorizing such seizures. The slaves were to be released in the nearest British port. The disposition of the ships was to be decided by British admiralty courts and the crews of such ships were to be returned to their own countries for trial.
By 1815 Britain, Russia, Austria, Prussia, France, the Netherlands, Sweden and the United States had agreed to prohibit the transatlantic slave trade.
Subsequently, Britain focused its attention on Brazil after its independence in 1822. In exchange for recognition by Britain in 1826, Brazil agreed to abolish the slave trade by 1830 despite strong opposition from many members of its parliament.
The treaty stipulated that the slave trade would be treated as piracy after that date, providing Britain with legal grounds for seizing slave ships on the high seas. Despite the agreement, slave trading continued between Brazil and Africa, even growing in the 1830s beyond what it had been before the treaty was signed.
Confronted with the continuation of the slave trade some 20 years after it should have been abolished under the 1826 treaty, Britain acted unilaterally. Slaving had already been declared piracy, giving British ships the right to hoard and seize suspected vessels on the high seas.
In 1850, British warships entered Brazilian ports and seized and burned a number of ships that were suspected of engaging in the transport of slaves. During these operations the British were fired upon from Brazilian forts. It is difficult to imagine a less ambiguous violation of the norm of non-intervention.
These pressures were effective. Confronted with British naval power and the antipathy of other advanced states, Brazil passed and enforced legislation to end the slave trade.
Brazil and Portugal were the most recalcitrant slave-trading countries. Portugal's colonies were both a major source of and point of sale for slaves.
One Brazilian leader speaking to the Brazilian Chamber of Deputies in 1850 recognized that Brazil was the only country actively resisting the antislave regime. He stated that:
"With the whole of the civilized world now opposed to the slave trade, and with a powerful nation like Britain intent on ending it once and for all, Can we resist the torrent? I think not."
The abolition of the slave trade was a triumph for human rights and freedom made possible in large measure by the commitment and power of Great Britain. Britain took the lead in initiating a series of international treaties in the early part of the 19th century that committed states to abolishing the slave trade.
Brazil was the most important defector from this system, failing to enforce its own treaty obligations. Britain used naval power including entry into Brazilian territorial waters and the destruction of Brazilian ships to compel Brazil to change its policies. .
_______