The Mycenaean civilization flourished in the Aegean during the Late Bronze Age, and reached its zenith between ca. 1400 and 1200 BC. Around 1200 BC, many of the Mycenaean centres were destroyed by fire. This period was one of great upheaval throughout the eastern Mediterranean, and also witnessed the destruction of the city-state of Ugarit, the fall of the Hittite Kingdom, and attacks against Egypt by so-called “Sea-Peoples” (for details, refer to Cline 2014).

Sometimes, the fall of the Mycenaean palaces is associated with the so-called “Dorian Invasion” (better: Dorian Migration); at other times, the Dorians are thought to have invaded at some other point during the Dark Ages, the period between the fall of the Mycenaean palaces and the rise of the Greek city-state in the historic era. Until the late twentieth century, there have been many attempts on the part of modern scholars to understand and date the Dorian Invasion, but no serious academic today would contend that it really happened.

The ancient Greeks of the historic era invented the migration of the Dorian to explain the contemporary distribution of ancient Greek dialects. The ancient Greeks usually distinguished between three main dialects – Ionian, Aeolian, and Dorian – and the Dorians were thought to have been relative newcomers. The problem is that there is little evidence for the presumed migration of Doric-speaking Greeks from somewhere north of the Peloponnese, and the Greek story may not be any more historical than the tales told about the demigods Perseus and Heracles.

Regarding the Dorian question, Oliver Dickinson sums it up well in his The Aegean from Bronze Age to Iron Age (2006), p. 11:

Sometimes, the ‘Dorian invasion’, ‘Ionian migration’ and related population movements reported in the Greek traditions have been treated as historical events that can be approximately dated and used as chronological signposts in the earlier part of the period. But, even if these traditions could be accepted as containing genuine information, the basis for dating them is shaky indeed. […] such movements were essentially dated by reckoning downwards from the Trojan War, but this was not fixed; very varied dates were calculated for it by ancient scholars, all of whom must have based their work on varying interpretations of the genealogies that linked historical persons with famous heroes. But it has long been recognised that these genealogies, among which those of the Spartan royal families are the best known, are too short to fit any possible chronology, if the ‘age of heroes’ is assumed – though this is a very questionable assumption – to have a historical basis in the world of the Mycenaean palaces […].

Jonathan Hall, in the second edition of his History of the Archaic Greek World (2014), has an entire section entitled “Gauging the historicity of the Dorian Migration” (pp. 44-51). He discusses the problem at length before reaching a conclusion very similar to what Dickinson wrote (p. 51):

There can be little doubt that the collapse of the political and economic system centered on the Mycenaean palaces provoked a climate of instability and insecurity and that some people – whether for reasons of safety or economic necessity – decided to abandon their former homes and seek a living elsewhere. But it is also clear that the developed literary narrative for the Dorian migration is the end product of a cumulative synthesis of originally independent traditions. As such, it need not reflect a dim and hazy memory of a genuine single movement of a population from north to south, even if it captures the general instability and mobility of this period. Rather, it seeks to establish a common identity for a plethora of communities whose pedigrees were undoubtedly far from uniform in origin.

In short, there is little merit to the idea that the Dorian Invasion, as a single movement of people, ever happened, and so we rate this claim as false.