Pelasgians or Pelasgi is the term applied to early populations of the Aegean, prior to the Flood of Deucalion and subsequent arrival of the Hellenic peoples to the region. Pelasgian Greeks are recognised as having occupied Crete at the end of the 2nd millennium BC. It is unclear from classical sources(b) exactly what regions the Pelasgians occupied, not to mention when or where they originated.
Some writers such as Densusianu have postulated a Pelasgian Empire extending over a large stretch of central Europe.
Euripides stated that the Pelasgians were later called Danaans.
Spiro N. Konda believes that today’s Albanians are descendants of the Pelasgians and has written The Albanians and the Pelasgian Problem in support of this idea, unfortunately, it is in Albanian, but some of his arguments can be read, in English, online(a).
Oliver D. Smith in his book Atlantis in Greece identified “the Pelasgians with both the Atlanteans and prehistoric Athenians – as two regional tribes at war with each other”.
A more radical, highly speculative and quite incredible, alternative definition is offered by Marin, Minella and Schievenin[0972.471], which is that Pelasgians were refugees from their homeland in Antarctica after its catastrophic destruction. They claim that these refugees were also known as Titans, Tyrrhenians and Atlanteans, among other names! They further claim that anthropology calls them Cro-Magnon!
(c) https://archive.org/details/in.ernet.dli.2015.283059/page/n33/mode/2up (2nd. Edition, Vol.II, p.8)
Nationalism was clearly the motivation behind some of the Atlantis theories that have been proposed over recent centuries. Olaf Rudbeck audaciously promoted his native Sweden in the 17th century, just as the eccentric William Comyns Beaumont claimed that Britain was Atlantis in the early 20th century and some Albanians, Azoreans, Maltese and Sardinians make comparable claims today. However, the most sinister manifestation of Atlantis based nationalism was the attempt to hijack it as the original homeland of the Aryan predecessors of the Nazis, probably borrowing the idea from Blavatsky. This was partly to replace the Abrahamic cultural lineage claimed by so many western nations. Today elements of modern Russian nationalism also look to an Aryan ancestry based in the Arctic.
*The linking of nationalism with (pseudo)archaeology is exemplified by the Bosnian pyramid claims of Samir Osmanagich and the manner in which the local media and politicians have used them to boost national pride, in spite of the contrary views expressed by qualified geologists and archaeologists(b).*
Vanessa Ward gives a good overview of the Atlantis based nationalism of both Rudbeck and the Nazis(a).