For several years, America — as well as other countries — had been paying a yearly tribute to the Barbary States of Algiers, Morocco, Tunis, and Tripoli in North Africa as protection insurance against pirates. But in 1800, the dey (or leader) of Algiers humiliated the U.S. ship that brought the tribute by forcing it to fly the flag of the Ottoman Empire while in Algiers Harbor.
The action angered American officials and hastened the building of naval ships that the penny-pinching Jefferson administration had only reluctantly supported.
The following year, the pasha (or leader) of Tripoli declared war on the United States because it wouldn’t increase its tribute. Over the next four years, the fledgling American navy dueled with the pasha and his pirates with mixed success.
Then in 1805, William Eaton, the former U.S. counsel to Tunis, led a motley force of about 200 Greek and Arab mercenaries — and 9 U.S. Marines (which is where the “to the shores of Tripoli” line in the “Marines’ Hymn” comes from) — on a 600-mile desert march.
Eaton’s force captured the city of Derna. Coupled with the presence of American warships off its harbors, Tripoli was forced to sign a peace treaty, free the American prisoners it was holding, and stop exacting tribute.
Although fighting with other pirates continued off and on for another six or seven years, the victory was a huge shot in the arm for American morale. But the real foreign threat about to surface was from a more familiar source.