There was a general collapse of civilization around the Eastern basin of the Meditteranean during the Late Bronze Age (1200-900 BCE) that saw the rise of unrest and raiding. The Sea Peoples were either acting separately or as a confederation of tribes in carrying out well-planned and large scale raids on the remaining city states.
Although much of their origins and history are shrouded in mystery, we do have several surviving records of their existence primarily from Egyptian sources.
What is irrefutable is that they made a lasting impact on the Late Bronze Age.
