Upvote:8
Greatly exaggerated, but basically correct for a video game.
You are correct that a fire ship is a ship deliberately set on fire, and possibly filled with explosives, and sent into an enemy fleet to set fires or to simply cause chaos. They were a powerful tactic against an enemy fleet in port to force a battle. They have been used through naval history.
How historically accurate is the use of flamethrower-style naval weaponry from states in Western Europe during the 1000-1400 AD time period.
Thucydides reports the use of some sort of flamethrower to set fire to Delium in 424 BC, though that was a land battle.
Battle at sea in this era was largely fought as little land battles with ramming and boarding being prominent. A ship's have fore and after "castle" was literally that, tall, heavily fortified towers on the fore and aft of a ship which could dominate the decks below. These fights could take days as in the final battle of HMS Revenge (1591). It makes sense that sailors would adapt the very terrifying, but very short ranged, flamethrower to naval combat. The 12th Century Madrid Skylitzes depicts naval flame throwers used by the Byzantines.
However, this was not a common practice. It existed, but not in numbers depicted in game. By 1000 its use was already waning. Throwing flaming pots with conventional artillery (ie. catapults) would be much more practical, and cannon would soon be common.
Using hand pumped pistons, they would not have the range to shoot flame against targets on the shore, maybe cinders could start fires on rooftops if the wind was strongly in their favor. Modern man-portable flamethrowers have a short range of about 20 meters. The game depicts something closer to a modern vehicle mounted flame thrower which can have an effective range of 100 to 200 meters.
The Far East? (China, Korea, Japan)
Their version of the Madrid Skylitzes is the Wujing Zongyao which depicts various fire weapons and a pumped flamethrower with detailed instructions.
The Battle of Langshan Jiang (919) featured use of a pumped flamethrower, taking care to be upwind of their target. The Song Dynasty made use of flamethrowers for centuries.
They would be more common than in the west, but not a common feature of naval battles.