A letter of marque is a government-issued document that allows a private ship owner to attack and capture enemy vessels during wartime. This practice was common from the 16th to the 19th centuries, enabling privateers to act on behalf of their country. The letter provided legal protection, distinguishing privateers from pirates, who operated without official sanction. These letters were often issued during conflicts, such as the War of 1812 or the American Revolutionary War. By granting this authority, governments could bolster their naval power without the expense of maintaining a large fleet. The captured ships and cargo would then be shared between the privateer and the government.