As part of the Webster–Ashburton Treaty of 1842, it was agreed that both countries would work together on the abolition of the slave trade, which was deemed piracy, and to continue the blockade of Africa.

[3][4] In 1815, Portugal strengthened their anti-slavery legislation by abolishing all trade north of the equator, allowing the Royal Navy a much freer hand.

The UK's slave trade suppression efforts attempted to remain within the primitive international laws of the time: slavers had to be tried in courts.

[7] In addition to the issues with Mixed Commission Courts, the Navy's mandate to police the trade was also found to be lacking and built on a series of complicated and often weak diplomatic treaties between other states.

This major flaw, which greatly curtailed the navy's efforts and caused some naval officers to fall foul of the law, was not rectified until the 1830s.

This caused several diplomatic incidents, as frustrated officers would often board ships with US flags, directly contravening their orders, to capture slavers.

There was fierce opposition to this in the US Congress, and John Forsyth said in 1841 that "the persistence" of British cruisers was "unwarranted", "destructive to private interests", and "[would] inevitably destroy the harmony of the two countries".

Brazil continued to defy British intervention, and the Brazilian trade was not extinguished until 1852, when Palmerston began using force under the Pax Britannica doctrine.

The Liberian coastal Kru people were hired, which allowed the West African Squadron to patrol the coast of Africa effectively.

[citation needed] By 1818, the squadron had grown to six ships, with a naval station established in 1819 at what is now Freetown and a supply base at Ascension Island, later moved to Cape Town in 1832.

Public opinion was beginning to turn against the anti-slavery efforts due to their huge costs, the diplomatic repercussions they created, and the damage caused to other trade.

Although the plan had offered a long-term solution to the slave trade, the expedition ended in abject failure, with many of the Europeans falling ill.

Brazil was still one of the largest slave trading nations and continued to defy British diplomatic calls to put an end to the practice.

In 1846, Palmerston returned as foreign secretary and in 1850 permitted Royal Naval vessels to enter Brazilian waters in order to blockade slavers on both sides of the Atlantic.

[17] "For Palmerston … the naval campaign on the coast of Brazil had brought the long drawn-out saga of the Brazilian slave trade to a resolution within twelve months".

In the Lyons–Seward Treaty of 1862, the United States gave the UK full authority to crack down on the Atlantic slave trade when carried on by US ships.

Wary of offending slaveholders to the least degree, the Senate amended the proposed Senatorial Act, then passed it to the House of Representatives, where it was meticulously scrutinised.

Lieutenant Stockton also convinced the local African chief to relinquish land around Cape Mesurado, where Liberia eventually formed.

On 26 and 27 November 1842, aboard USS Somers in the African Squadron, commander Alexander Slidell Mackenzie ordered the arrest of three crewmen who were plotting to take control of the ship.

A small number of ships were accosted; some of them were carrying Africans destined to be sold into slavery, while others, which had no slaves on board, were captured and escorted away from the coast of Africa.

Jean Lafitte was a pirate who brought many slaves to the United States and sold them through an organised system established at New Orleans that included merchants from the vicinity.

After he helped Andrew Jackson during the War of 1812, President James Madison issued a proclamation early in 1815 granting him and his men pardons for their misdeeds.

Few new ships were built in the United States after 1801 until USS Guerriere was launched on 20 June 1814; it proved to be an effective warship in the war with the Barbary pirates in 1815.

At the same time as this effort was taking place, other important tasks, such as the War of 1812, the ongoing troubles with the Barbary pirates, the extermination of the pirates in the West Indies from 1819 to 1827, the protection of American shipping in the Pacific Ocean off the coast of Peru in the 1830s, the War with Mexico in the 1840s, the voyages to Japan in the 1850s, and transporting of diplomats to other nations left little capability available for use in the African Squadron.