What was the doric invasion?

The Doric invasion refers to the migration of the Dorian Greeks into the Greek mainland and parts of the Aegean islands around the end of the Mycenaean period, roughly in the 12th century BCE. This event is often associated with the decline of the Mycenaean civilization and the onset of the Greek Dark Ages. The Dorians are believed to have introduced new social and cultural practices, leading to significant changes in the region's Demographics and political structures. Their arrival is traditionally linked to the establishment of the distinct Doric dialect and the eventual rise of city-states like Sparta.