"Mediaeval scholars were pulled out of Oxford colleges and flown into Umbria."

The type of warfare needed to take this very clever and well-fortified towns was no longer in use, hence the need for mediaeval scholars.

http://en.wikipedia.org/wiki/Medieval_warfare

Luckily, we now have the internet with handy pages like this one on how to defend your medieval castle. http://www.ehow.com/how_4558988_defending-medieval-castle.html

If you're very interested you can learn mediaeval war skills in Sussex: http://news.bbc.co.uk/local/sussex/hi/people_and_places/newsid_8840000/8840777.stm