A privateer was a private individual or ship authorized by a government to attack enemy ships during wartime. This authorization, known as a letter of marque, allowed privateers to capture enemy vessels and claim their cargo as prizes. Unlike pirates, who operated outside the law, privateers acted with the backing of their government. Privateering was common in the 16th to 18th centuries, especially during conflicts like the Anglo-Spanish War and the American Revolutionary War. Many famous privateers, such as Sir Francis Drake, played significant roles in naval warfare, contributing to their nation's military efforts while also seeking personal profit.