Genomics data confirms that the Avars were of East Asian origin before taking over the Carpathian basin.
Historians have gradually accorded increasing respect to the various Central Asian groups that swept in and terrorized Europe for a millenium, including in turn the Scythians, Huns, Avars, Mongols, and Turks. The Mongols particularly created a golden age of commerce across the Silk Road, which Marco Polo traveled to such great adventure. This history is both extremely dynamic, and poorly documented, as these nomadic cultures left little behind, especially writing. Their roots range from Iran and the Indo-Europeans to the Mongolian and Tungusic regions. A putative "Altaic" language group extends from Hungary all the way to Korea and Japan, though it is a disparate group arising more from interchange and borrowing than from a single origin- testament to the frequent traffic along the steppes.
To settled cultures, both in Europe and in China, these nomads were terrors, living on their horses, infinitely mobile, and possessing powerful weapons like their composite bows. The continual succession of these cultures (unlike, say, the long stability of ancient Egypt) also indicates that they fought constantly among themselves, in true Darwinian fashion. Success revolved around not only technical innovation and a martial culture, but also social abilities to forge groups large and cohesive enough to control vast regions, despite the tendency of warriors to fight ... with each other.
The Avars were one of this succession, historically known as invaders of the Carpathian Basin who set up a brief empire (~570 to 790 CE) after defeating Goths who had in turn succeded the Huns, who had replaced the Romans of Pannonia. At their height, the Avars ruled from Turkey to Austria, but were within two hundred years defeated by the Franks, who were soon followed by the Magyars, who finally stayed to found what is now Hungary. One can see that the Balkans, which lie in this region and towards the Adriatic, have had a tumultuous history. The Avars had reputedly come from the far East, after the nascent Turks defeated the Hunnic / Rouran center, of which the Avars were supposedly a successor, offshoot, or client group. Historians have been divided, though, since there is little evidence of far Eastern influences in the Carpathian archeology, and competing accounts put their origin more Westerly, around the Urals or Caspian basin.
"The Rourans were defeated by the Turks, who had been their subjects, in 552–555. Their empire fell apart and, according to the contemporary Chinese sources, the core Rouran population was brutally massacred. Some of the Rourans fled to China and soon disappeared from sources. Another group of the Rourans is commonly thought to have migrated westwards and become the Avars of European history"
But a recent paper (largely authored by Hungarians) has settled the matter. They sequenced DNA from numerous burials dated through the Avar era, and compared them to a variety of samples from across the steppes. They find that indeed, the earliest and richest graves of the Avar era have almost exclusively far East Asian DNA markers, from what is now roughly Mongolia, while later remains show increasing admixture with the local Western Europeans.
"All of the early-Avar-period individuals (DTI_early_elite), except for an infant and a burial with typical characteristics of the Transtisza group, form a tight cluster with a high level of ANA (ancient North East Asian) ancestry. They are located between present-day Mongolic- (e.g., Buryats and Khamnigans) and Tungusic/Nivkh-speaking populations (e.g., Negidals, Nanai, Ulchi, and Nivkhs) together with the only available ancient genome from the Rouran-period Mongolia."
"The remaining 9 late-Avar-period individuals show minor (<40%) to almost negligible (<5%) admixture with ANA-related sources, while the major ancestry component can be approximated by one of the preceding local groups for most of the individuals"
In discussions of these eras, hundreds of years can go by rather quickly. Still, the mobility and dynamism of these peoples is astonishing. Rome had already experienced the knock-on effects of tribes such as the Scythians driving other peoples westward before them. And the Indo-European invasions were something similar, farther back in the mists of time. Such migrations and conquests kept on happening, thanks to the love these people had for their horses, the endless flatness of the landscape, and the rich pickings available among settled cultures around their periphery.
Today, Russia (whose lengthy period under Mongol rule strongly shaped its culture) has resumed the mortal competition for empire among the flatlands of Central Asia and Eastern Europe. While we can marvel at the relentless valor of Huns and Avars, seeing such ruthlessness up close in our own time isn't abstract history, it is thoroughly appalling.