10th May 1801: The First Barbary War began when Tripoli declared war on the United States

The Barbary States consisted of the modern countries of Algeria, Libya, Morocco, and Tunisia. Lying on the North African coast, the Barbary States were home to privateers who patrolled the Mediterranean and captured merchant ships. As well as seizing their cargo, the pirates would often either enslave the crew and passengers or demand a ransom for their safe return.

European nations such as Britain and France paid costly tributes to the local rulers to ensure their merchant vessels were left safe from the pirates. Prior to the Revolutionary War this arrangement also protected American vessels, but following independence from Britain the new United States lost this protection.

While the United States successfully negotiated a treaty with Morocco in 1786, the other Barbary States began capturing American vessels and demanding ransoms that the new government struggled to afford. Negotiators eventually relented and agreed to pay an annual tribute in order to maintain access to the valuable Mediterranean markets, while politicians including Thomas Jefferson argued that such an approach would only encourage further piracy.

When Jefferson became President in 1801 he immediately adopted a hard line against the Barbary States. Pasha Yusuf Karamanli of Tripoli had threatened war unless he received a dramatically increased tribute of $225,000, but Jefferson refused the demand. On 10 May 1801 the Pasha declared war on the United States by cutting down the flagstaff in front of the U.S. Consulate, sparking the First Barbary War. The conflict lasted until June 1805, but continuing tensions led to the Second Barbary War in 1815.