forum.freeciv.org

I suggest the introduction of a unit flag "privateer"

In colonization a player can build "privateer" units, which are controlled normally by a player. However, to all other players these units look like pirate/barbarian units.
"Privateer" units can attack and be attacked by all units without a declaration of war. Such units offer additional tactics and a player could fight an "undercover" war.

I like the idea, but presumably there should also be a mechanism for discovering the
paymaster? Perhaps if you bribed the unit, you would find out... if it retained the
nationality of the building city.

I have read that privater are available in Civilization III.