Even more important, however, were humanitarian concerns. At the Congress of Vienna, Britain pressed the other powers to bar the trade in slaves but achieved only a commitment in principle to its eventual abolition. Those profiting from slavery mocked the hypocrisy of British concern for African slaves while His Majesty's own subjects languished in involuntary servitude along the Barbary Coast. The taunts stung.

Then a British naval officer, Commander Walter Croker, visited Algiers. He wrote an incendiary letter decrying the "cruelties practiced on Christians of every nation, and of indiscriminate slaughter, involving our own countrymen." When sending the letter to a government minister failed to produce the desired effect, he published it, touching off a media firestorm. Parliament demanded action. William Wilberforce, an inveterate critic of slavery, condemned "the evils...which had been so long tolerated," and called for "cannon balls" instead of the payment of any ransom.

Admiral Lord Exmouth, the British commander in the Mediterranean, was dispatched to secure a solution. In Tripoli, he ransomed 468 slaves and secured a commitment to end the practice. Tunis, too, capitulated, ransoming some slaves, releasing others, and pledging at least to treat future captives as prisoners. Algiers, however, proved more defiant, and Exmouth retired to England in frustration.

The slaughter of some 200 fishermen from the Italian states provided a fresh impetus for action. Exmouth returned at the head of a powerful fleet. In Gibraltar, he met up with a squadron of Dutch frigates, and its commander pledged his support. They sailed, together, for Algiers and delivered their ultimatum. Receiving no response, they proceeded to bombard the fortifications, leveling half the city in the process. Exmouth demanded the Dey's surrender, distinguishing between the ruler and his populace by adding that as "England does not war for the destruction of cities, I am unwilling to visit your personal cruelties upon the unoffending inhabitants of the country." (It was a fine sentiment, but perhaps one that the inhabitants of the rubble of Algiers, slaves included, were poorly disposed to appreciate.) More than three thousand captives were released.

Back in Britain, Parliament congratulated Exmouth on a victory "most favourable to the interests of humanity," and the Duke of Clarence declared that British action had been "actuated by a pure feeling of humanity towards the rest of the world." Plays and pamphlets celebrated the triumph, and Britain engaged in an extended bout of self-congratulation.

Over the longer term, though, the results of the expedition proved more equivocal. The offending rulers were not deposed. Piracy and slavery declined, but neither immediately disappeared. European intervention in North Africa would only escalate in the decades that followed.