European maritime powers paid the tribute demanded by the rulers of the privateering states of North Africa (Algiers, Tunis, Tripoli, and Morocco) to prevent attacks on their shipping by corsairs. No longer covered by British tribute payments after the American Revolution, United States merchant ships were seized and sailors enslaved in the years that followed independence. In 1794 the United States Congress appropriated funds for the construction of warships to counter the privateering threat in the Mediterranean. Despite the naval preparations, the United States concluded a treaty with the dey of Algiers in 1797, guaranteeing payment of tribute amounting to US$10 million over a twelve-year period in return for a promise that Algerian corsairs would not molest United States shipping. Payments in ransom and tribute to the privateering states amounted to 20 percent of United States government annual revenues in 1800.

The Napoleonic wars of the early nineteenth century diverted the attention of the maritime powers from suppressing what they derogatorily called piracy. But when peace was restored to Europe in 1815, Algiers found itself at war with Spain, the Netherlands, Prussia, Denmark, Russia, and Naples. In March of that year, the United States Congress authorized naval action against the Barbary States, the then-independent Muslim states of Morocco, Algiers, Tunis, and Tripoli. Commodore Stephen Decatur was dispatched with a squadron of ten warships to ensure the safety of United States shipping in the Mediterranean and to force an end to the payment of tribute. After capturing several corsairs and their crews, Decatur sailed into the harbor of Algiers, threatened the city with his guns, and concluded a favorable treaty in which the dey agreed to discontinue demands for tribute, pay reparations for damage to United States property, release United States prisoners without ransom, and prohibit further interference with United States trade by Algerian corsairs. No sooner had Decatur set off for Tunis to enforce a similar agreement than the dey repudiated the treaty. The next year, an Anglo-Dutch fleet, commanded by British admiral Viscount Exmouth, delivered a punishing, nine-hour bombardment of Algiers. The attack immobilized many of the dey's corsairs and obtained from him a second treaty that reaffirmed the conditions imposed by Decatur. In addition, the dey agreed to end the practice of enslaving Christians.

Data as of December 1993