A commission issued in Britain by the Lord High Admiral, or by commissioners executing his office, and by the equivalent authorities in other countries, licensing the master of a privately owned ship to cruise in search of enemy merchant vessels, either as reprisal for injuries suffered or as acts of war. Ships so licensed were themselves also sometimes referred to as letters of marque, though more usually called privateers. The earliest mention of such a letter is in 1293 and they continued to be issued in time of war or of reprisal until privateering was abolished at the Convention of Paris in 1856.
The practice of licensing privateers by special commissions was very often a highly profitable affair and many owners were anxious to equip their ships with guns in wartime to prey on such merchant shipping as they could come across. In spite of the official commissions they carried, acts of piracy were common. It was a form of warfare at sea much criticized by all navies, as the rewards of a successful privateering voyage were often so great they attracted seamen away from service in regular warships.
Subjects: Maritime History — Warfare and Defence.