Late Bronze Age

1000 BC (3000 Years Ago) — Society became more warlike and stratified. Large hillforts were constructed as defensive strongholds for tribal leaders.

As the Bronze Age progressed, society became increasingly warlike. The simple tools of the early period gave way to advanced weaponry: slashing swords, socketed axes, and shields. To defend themselves and their wealth, tribal leaders built massive hillforts, such as Dún Aonghasa on the Aran Islands and Haughey's Fort in Armagh.

The climate began to deteriorate, becoming wetter and cooler. This led to the rapid growth of peat bogs, which reclaimed much of the farmland cleared by earlier generations. While this was a disaster for Bronze Age farmers, it was a boon for modern archaeologists, as the anaerobic bog preserved wooden tracks, butter, tools, and even "bog bodies"—sacrificial victims killed and placed in the bog.