Privateers were licensed raiders, and one missing document could turn them into pirates
For centuries a government could hand a private shipowner a paper called a letter of marque and send him to seize enemy cargo for profit. With the paper he was a patriot sharing prize money with the crown. Without it, or after peace was signed, the very same act could get him hanged as a pirate.
A commission typically named a single ship, its officers and a time limit, and owners often had to post a bond. It also specified which nationalities counted as enemies. A captain had to show the document to any ship he stopped; seizing a vessel from a nation not at war with his sponsor was piracy. Captured ships went before prize courts and were sold, with proceeds split among investors, owners, captain and crew, and usually a cut for the sovereign.
The arrangement suited everyone for a while. States could expand their fighting fleets cheaply when taxes could not fund a professional navy, and sailors on privateers were paid in shares of the loot rather than wages, offering working seamen a shot at real wealth. Investors packed ships with far bigger crews than merchantmen carried, so there were hands to sail captured prizes home. In the first Anglo-Dutch War, English privateers seized more than 1,000 Dutch merchant ships, and Spanish-backed raiders later took 1,500 English ones.
The boundary with piracy was always blurry. Many crews simply kept raiding when wars ended. A New York governor issued commissions to Thomas Tew to fight the French, only for Tew to go after Mughal shipping in the Red Sea instead. William Kidd, commissioned by King William III to hunt pirates, was hanged for piracy after failing to produce papers proving his captures were lawful. English law also shifted, treating piracy first as treason under a 1536 act and later as a property crime.
Industrial-era navies and the modern state's grip on violence ended the practice. In the 1856 Declaration of Paris, every major European power declared the practice permanently finished. Washington refused to sign, wanting broader protection for private property at sea, but has not commissioned a privateer in any war since. Prussia's volunteer navy of 1870 was the last major flirtation.
Source: Privateer
