Hill forts developed in the Late Bronze Age and Early Iron Age.
See:
- https://en.wikipedia.org/wiki/Maiden_Castle,_Dorset
- http://www.historic-uk.com/HistoryMagazine/DestinationsUK/Maiden-Castle/
- Ian Armt, Hillforts at war: from Maiden Castle to Taniwaha pā in: Proceedings of the Prehistoric Society 73, 2007, pp. 25-38 - https://www.academia.edu/9722868
- http://www.oppida.org