Although invented by the scientists of the Empire, Ironfists are used both by and against many of the nations of the Old World, for whenever cities are built beside a river the Ironfist can bring immense firepower to bear on an otherwise inaccessible position.[1a] On occasion, however, Ironfists have been used to great effect in a number of famous sea battles. In such confrontations the Men O' War and Ships of the Line advance toward their prey, while the Ironfists in the rear lay down a screen of heavy duty cannonballs.[1a]