Students of military history know that there are fifteen proven ways to defend a walled city. Unfortunately they all require things like catapults, weaponry, and soldiers. What the capitol of the Robur empire has are nice thick walls, five hundred watchmen, a few gardeners, some gladiators, and the Corps of Engineers led by Colonel Felix Orhan. Sadly, they also have an enemy that numbers thirteen thousand with the best armor and swords the empire can buy. Felix could run away and become a farmer somewhere, or even join the enemy since they are also pale skinned "barbarians", but he chooses the third option which involves making up a sixteenth method for defending a walled city.