For several centuries, the Barbary pirates were the very definition of terror on the high seas as they pillaged northern Africa's Mediterranean Sea and even north along Europe's Atlantic coastline. Ruthlessly adept at plundering passing merchant ships, the Barbary pirates often acted as a united political and military force, with enough influence to demand ransoms and tributes from the most powerful nations. At various times from the fifteenth to the seventeenth centuries, Spain, France, Portugal, the Netherlands, and even the fledgling United States paid exorbitant fees to appease the demands of Barbary pirates.