8 U.S. Marines400–500 Arab The Battle of Derna at Derna, Cyrenaica, was the decisive victory in April–May 1805 of a mercenary army recruited and led by United States Marines under the command of U.S. Army Lieutenant William Eaton, diplomatic Consul to Tripoli, and U.S. Marine Corps First Lieutenant Presley Neville O'Bannon.

[1] The Battle of Derna and the broader First Barbary War highlighted the challenges faced by the United States in dealing with piracy and asserting its interests in the Mediterranean during the early years of its existence as a nation.

In 1804, the former Consul to Tunis, William Eaton (1764–1811), returned to the Mediterranean Sea with the title of Naval Agent to the Barbary States.

Eaton had been granted permission from the United States government and President Thomas Jefferson to back the claim of Hamet Karamanli, the rightful heir to the throne of Tripoli who had been deposed by his brother Yusuf Karamanli, who had assassinated his older brother by shooting him in front of his mother.

[5] On March 8, 1805, Lieutenant Eaton led his forces on a 500 miles (800 km) trek westward across the Libyan desert from Egypt.

During the 50-day trek, Eaton became worried over the strained relationship between the Christian Greeks and the roughly 200 to 300 Muslim Arab and Turkish mercenaries.

Hamet was to lead the Arab mercenaries southwest to cut the road to Tripoli, then attack the city's left flank and storm the weakly defended governor's palace.

On the Argus, Captain Hull saw the Americans and mercenaries were "gaining ground very fast though a heavy fire of Musquetry [sic] was constantly kept upon them."

Eaton would report that O'Bannon with his Marines and Greeks "pass'd through a shower of Musketry from the Walls of houses, took possession of the Battery."

O'Bannon raised the American flag over the battery (the 15 stars, 15 stripes emblem used from 1795 to 1818, later made famous in the War of 1812 as the "Star-Spangled Banner"), and Eaton turned the captured guns on the city.

By 4:00 p.m. the entire city had fallen, and for the first time in history, an American flag flew over fortifications on the opposite side of the Atlantic Ocean.

Eaton fortified his new position, and Hamet took up residence in the governor's palace and assigned the Arab mercenary forces to patrol the outer areas of the city.

[10] It was the decisive action of the First Barbary War (1801–1805) although Eaton was furious over what he called a "sell-out" between the State Department diplomat Tobias Lear and the bey.

The first mention of Hamet giving O'Bannon a bejeweled sword seems to be in a lengthy article, "Kentucky Officer First to Carry Stars and Stripes to Victory in Foreign Country," by John Presley Cain in the 29 July 1917 edition of the Louisville Courier-Journal.

A further legend holds that O'Bannon's exploits in North Africa inspired the Marine Corps officers to adopt Mameluke swords, but that is also uncorroborated by any contemporaneous sources.