In Europa Universalis II, Pirates are spontaneously-generated or player-generated naval forces which are the enemy of all countries.
Pirate Attributes Edit
Pirates are in some ways handled like a country. While they cannot own provinces and thus have no income as such, they have a naval technology level and they are in the latin techgroup, so they will get high neighbor bonuses from the European countries. Also they have a "monarch" with a military stat of 7, a source of direct investment that is quite powerful for a small "country". Thus, pirates' naval tech level tends to trail the leading latin tech level by 2 to 5 levels. This makes them fairly difficult opponents for most non-latin countries. Pirates also gain victory points and may show up on the VP board (F1). If a spot among the top ten nations seems to be not occupied it may well be them. Pirates have their default domestic policy sliders all set at 5.
Pirate Effects Edit
Like other fleets, pirate ships will engage enemy naval forces in battle. The chances are low for fleets only travelling through a pirate-infested sea zone, but high for a fleet that stops there. Pirates moving into a seazone where a regular fleet is stationed will (always?) attack it.
When you beat them in battle, surviving pirate ships retreat to some adjacent sea zone. Pirates also occasionally move to an adjacent sea zone on their own.
Pirate Generation Edit
Pirates are randomly generated (as a built-in event) in empty coastal sea zones, at each month's end. 1-4 pirates are generated, and they only use warships (no galleys or transports). The chance of this happening is very small in any given sea zone per month. However, with time and many sea zones, especially at the peak of piracy in the Caribbean (1600s), pirates rapidly get numerous unless dealt with.
The player can also create pirates, by hiring privateers. See below. AIs don't hire privateers.
Handling Pirates Edit
One way to handle pirates if you have reasonable naval tech is to create a massive anti-pirate force and put it on patrol.
If there is any fleet in a sea zone, pirates cannot be generated there, although they can still move there from adjacent provinces. Many players place a token fleet (usually a single galley) in every province of national waters, thereby preventing pirate generation.
Privateers are pirates that the player can commission. Privateers can only be commissioned in a sea zone that currently lacks pirates. To do so, select the sea zone and press the "hire privateer" button in the info screen. The cost is 25d.
(This is a little-used function because there are few good uses for commissioning privateers. Privateers may be used to assassinate rival explorers, if you catch sight of them in a small fleet.)