[quote=Iarumas]
If I want to make use of my Greek Fire, I do not need the War Engines trait right? It's usable on jsut basic siege equipment?Also, if we want to deploy siege engines on the battlefield and not necessarily on an actual siege can we without the War Engines trait?
[/quote]

You don't need the War Engines trait no for Greek Fire, though you need to use something like Trebuchets instead of a standard tension based catapult, mangonel or ballista. (Shattering pots etc)

And Gat's got the right of it, War Engines are basically primitive tanks. Like those that Leonardo Da'Vinci conceptualised (except with no cannon, instead Ballista or Catapults etc.)

Light ones would be similar to da-vinci's designs. Heavy would be like Warhammer Fantasy's Steam Tanks.