Most of the castles which were built by the Normans were not constructed until about one hundred years after their arrival. Some stone castles, of course, were built in this early period but most of them were probably built between the end of the thirteenth century and the middle of the fourteenth century, while a small number were built as late as 1500 to 1550. These castles were located in such a way as to allow easy access to one another for defensive purposes during the times of attack. Each castle in the area was within radius of 2-3 miles of at least two more, and therefore, in the event of attack, a fire lit at the parapet of one, was a signal to the others.
– The History & Folklore of Killenaule/Moyglass 1990