Fortifications are usually a result of the weapons tech and threat an invading army poses. The introduction of gunpowder saw a significant change in fortifications so my question is how would one go about fortifying against dragons? In my story dragons don't get huge the largest might weigh a little more than an African elephant but still having a fire spewing African elephant attacking my town is not something I would like. After that they get smaller, I have wild dragons that are much smaller and much more agile and aggressive but the domesticated ones have been breed to serve diverse combat roles much the way horses or dogs have been breed. They don't have ipenetrable hides and can be killed but their hide is think like that of a rhino. and the last thing dragons are expensive so an army of 1k might have at most 50. They are more expensive that a war horse would be in the middle ages. In terms of fortifications the only thing I can think of is towers with Roman balistae on top. Smaller towns are on their own I would think. Also doing this for something like a castle is one thing what about fortifying a city the size of Rome? Also in an open field battle how would dragons change the battle? and how would you attack an army with dragons?