Mycenean Greece, the home of Homer’s Agamemnon, flourished after the decline of the Harappan civilization.This culture showed great affinity with that of the Minoan culture which predated it and displayed warlike character similar to the Spartans (the folks in 300). The Mycenean palaces were fortified and warfare paintings dominated their wall paintings.
This civilization collapsed around 1100 B.C.E and the collapse was attributed to the Dorian Invasion. According to this theory, a group of Greek speaking men from the North invaded the Peloponnese peninsula and destroyed the Mycenean civilization. As per the Greek tradition, this movement was the return of the sons of Heracles, who were the founders of three Dorian (from the city of Doris in central Greece) tribes.
The early descriptions of the Dorians came from Herodotus, who himself was from a Dorian colony and wrote that the Dorian women wore a particular kind of dress which was fastened with pins. Thucydides dated the Dorian invasion to 80 years after the Trojan war and wrote that the Dorians held the Peloponnese implying military activity.
Archaeologists after reading Herodotus and Thucydides looked for the dress pins and found a few. It seems there was an ideological movement in the 19th century to emphasize the war like nature of the Dorians and distinguish them from the Peloponnese . While classical historians put the origins of Dorians near Thessaloniki, 20th century historians moved them far north and gave them blue eyes and blonde hair.
The similarity to the Aryan invasion/migration theory which states that war like Aryans from Central Asia invaded ancient India around 1500 – 1200 B.C.E is remarkable. The Aryan invasion theory was put to rest when genetic studies found that there was no massive movement of Central Asians in that time frame and no external origins to Indian castes and tribal population. Genetic studies of Indian populations also told us that Indo-European speakers reached India much before the fictional date and were not foreigners by the time the vedas were composed.
In the Peloponnese case, decipherment of Linear B, the script used for writing Mycenaean, revealed that it was Dorian in style and thus the invaders suddenly turned into a linguistic sub group. The question then was if the Dorians were newcomers or the old population adapting to new conditions of the Iron age. History Professor Isabelle Pafford calls it the invasion by safety pins since the earlier invasion theory has now been discredited.