"Letters of Marque" - Papers issued by a national government during wartime, entitling a privately owned ship to raid enemy commerce, or even attack enemy warships. Early letters of reprisal were issued to merchants to make it legal for them to counter-raid pirates. A ship bearing such letters, and operating within their limits, is a *privateer* rather than a pirate (i.e., a legal combatant rather than a criminal and murderer)