[4] Hillforts developed in the Late Bronze and Early Iron Age, roughly the start of the first millennium BC.

It has been argued that they could have been military sites constructed in response to invasion from continental Europe, sites built by invaders, or a military reaction to social tensions caused by an increasing population and consequent pressure on agriculture.

Deposits of iron ore were located in different places to the tin and copper ore necessary to make bronze, and as a result trading patterns shifted and the old elites lost their economic and social status.

[6] Archaeologist Barry Cunliffe believes that population increase still played a role and has stated "[the forts] provided defensive possibilities for the community at those times when the stress [of an increasing population] burst out into open warfare.

They would be functional as defensive strongholds when there were tensions and undoubtedly some of them were attacked and destroyed, but this was not the only, or even the most significant, factor in their construction".