France was the first country to free its slaves, when they took the liberty, equality and fraternity literally in 1794, following the French Revolution. Unfortunately Napoleon Bonaparte (who some people seem to admire for some reason) actually reintroduced slavery in 1804. Britain was able to force the French to abandon the slave trade after the war in 1815 (but the French did nothing to enforce the ban until 1848). There was a big move at the end of the Napoleonic Wars to end the Slave Trade worldwide. Tom Pockock's book 'Breaking the Chains: The Royal Navy's War on White Slavery' relates the action in the Mediterranean culminating in the battles at Algiers, Acre and Navarino.

Actually, Denmark banned the trade in slaves from 1803, although they did not have the same facilities as the British to enforce the ban.

Probably the countries most desirous of maintaining the slave trade were Portugal, Spain and Brazil. It took subsidies of over four million pounds sterling to convince the first two to desist and the threat of military action for the last-named to ban the trade.