"Let the colonies perish rather than a principle!" Such was the generous command which resounded through all the Old World, and, in spite of the great political and commercial interests engaged in the question, it was effectively transmitted through Europe.
The impetus was given.

In 1807, England abolished the slave-trade in her colonies, and France followed her example in 1814.

The two powerful nations exchanged a treaty on this subject--a treaty confirmed by Napoleon during the Hundred Days.
However, that was as yet only a purely theoretical declaration.

The slave-ships did not cease to cross the seas, and to dispose of their "ebony cargoes" in colonial ports.
More practical measures must be taken in order to put an end to this commerce.

The United States, in 1820, and England, in 1824, declared the slave trade an act of piracy, and those who practised it pirates.
As such, they drew on themselves the penalty of death, and they were pursued to the end.