Which conflict was the first recorded land battle of the United States fought overseas?

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, (1764-1811), diplomatic Consul to Tripoli and U.S. Marine Corps First Lieutenant Presley Neville O’Bannon (1776-1850).

The battle involved a forced 500-mile march through the North African desert from Alexandria, Egypt to the eastern port city of Derna, Libya, which was defended by a much larger force.

Following a bombardment by the U.S. Navy's Mediterranean squadron, an inspired charge sent the defenders running, and gave victory to the invading force.O'Bannon raised the American flag over the battery (the unique 15 stars - 15 stripes emblem used 1795-1818, later made famous in the War of 1812 as the "Star-Spangled Banner"), and Eaton turned the captured guns on the city. Hamet's force had seized the governor's palace and secured the western part of the city. Many of the defenders of the harbor fortress fled through the town and ran into Hamet's force. 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.

The Battle of Derna was the first land battle of the United States on foreign soil, after the American Revolutionary War (1775–1783).

The attack on Derna was also the inspiration for the lyrics of the Marines' Hymn in the line - "to the shores of Tripoli".