Getae and Dacians? Are they the same? Or is this unknowable?

[Alanus]

Through archaeology and steppe art, we know that the Massagetae were Northeast Iranian in culture and language. In the bronze age they moved east across southern Russia; and by the iron age they were well established in the Altai, where they left numerous traces.

So we can be sure of three things:
1- The Massagetae originally came from Iran.
and
2- A number of Iranian tribes moved up into the steppes sometime around of the 1st millenium BC. Some went northeast like the Massagetae, some went northwest like the Sarmatians.
3- There was a tribe Herodotus called the Thyssagetae living somewhere near the southern tip of the Ural mountains.

Maybe there were a few different "-Getae" tribes that went separate ways when leaving the Iranian heartland, and one of them ended up near the Danube?
And the Dacii may have been a different tribe? Maybe the Getae became assimilated into the (more established?) Dacii, and their ancestral name fell out of use during the five-or-so centuries that passed between the time Herodotus wrote and Trajan's conquest?

Or maybe there's nothing to this, and they are actually just two names for precisely the same people?
Or maybe this is unknowable?
I'm leaning toward the latter.

They then moved southwest across the Jungar Pendi and along the north of the Tian Shan. Russian archaeologists have determined that many individuals had significant Asiatic features. They became known to the Persians as the Saka or Sacae, and then called the Massagetae by Herodotus. When we reach Dio and then Ammianus, we hear statements like "The Alans were formerly known as the Massagetae," and "The Alans are the Massagetae."

The Saka/Massagetae/Alan culture always was Iranian and always spoke Northeastern Iranian.

And just to add further confusion, in The Vandalic War Procopius wrote "the Massagetae whom they now call Huns."

Hello Justin of New Yorkii,

This appears as more or less the scenario, according to archaeology. But do remember that there was no "Iranian heartland" and the Massagetae/Alans were not related to the Iranians, aka Persians. It's better to think of the original geographical location (southern Urals to Caspia) as the "Indo-European homeland," since the peoples who migrated from it included not just Iranians, but Indus and Europeans. The closest tribes to the Massagetae and Thyssegetae were the Scythians and Sauromatae, the last of whom Herodotus explains as marrying "Amazons" (a female Massagetae war-band.) The Scyths faded, and the Sauromatae (mostly Iazyges) moved up onto the Hungarian Plain (the last steppe).

There can hardly be any correlation between the Massagetae and the Dacians. The Massagetae/Alans controlled the steppe and built a huge empire (coveted by Cyrus) which lasted for six hundred years. The Dacii were a small tribe (in the greater scheme). Perhaps a forebearer of terrors to come, the lead Alan groups-- the Roxolani and Taifali-- arrived in Dacia after the Romans trounced it. Combined with the Goths, the Taifali and Roxolani, "devistated" Dacia. I cannot see how the Dacian culture could have been influential after the second century.

Procopius was referring not to the Black Huns but the White Huns (Ephthalites) when he called them "Massagetae." They were living in the old domains of the original Saka/Massagetae near Bactria and Sogdiana.