Definition
A "letter of marque" is a government license authorizing a private citizen to outfit an armed vessel and use it to attack enemy ships during wartime. Essentially, it's a license to be a legal pirate 🏴☠️. Think of it as a temporary naval commission granted to private individuals. Historically, it allowed nations to supplement their navies. The practice blurred the line between privateering and piracy. Nowadays, the practice is largely obsolete due to international laws and treaties. So, it's a historical relic from a time when governments sanctioned privateering.