This was true in ancient Greece, although you wouldn’t know it from ancient Greek historians, for whom the polis, or independent Greek city-state, symbolized the demise of kingly oppression and the rise of citizen equality and civic pride. For instance, neither Herodotus nor Diodorus Siculus mentioned mercenaries in their reports of the first Battle of Himera, a fierce struggle in 480 B.C. in which the Greeks from various Sicilian cities united to beat back a Carthaginian invasion. Mercenaries were considered the anтιтhesis of the Homeric hero.

“Being a wage earner had some negative connotations — avarice, corruption, shifting allegiance, the downfall of civilized society,” said Laurie Reitsema, an anthropologist at the University of Georgia. “In this light, it is unsurprising if ancient authors would choose to embellish the Greeks for Greeks aspect of the battles, rather than admitting they had to pay for it.”

But research published on Monday in the Proceedings of the National Academy of Sciences suggests that the ancestry of the troops defending Himera was not as strictly Greek as historical accounts of the time would have it.

The victory was widely seen as a defining event for Greek idenтιтy. But the new study, an analysis of degraded DNA from 54 corpses found in Himera’s recently unearthed west necropolis, found that the communal graves were largely occupied by professional soldiers from places as far-flung as those known today as Ukraine, Latvia and Bulgaria.

The finding ʙuттresses research published in 2021 in which Katherine Reinberger, a bioarchaeologist at the University of Georgia, and her colleagues performed a chemical analysis of the tooth enamel of 62 fallen fighters buried near Himera’s ancient battlefield, where two major clashes played out: one in 480 B.C., when Himeran forces defeated the Carthaginian general Hamilcar Mago, and a second battle seven decades later, when Hamilcar’s grandson returned for revenge and Himera was destroyed. Dr. Reinberger’s team concluded that about one-third of those who fought in the first conflict were locals, compared with three-fourths in the later battle. Dr. Reitsema is a principal author on both studies.

Angelos Chaniotis, a Greek historian at the Insтιтute for Advanced Study in Princeton, said the new study cast new light on the composition of the battles at Himera, if not on their outcomes. “It confirms the general picture that we had from ancient sources, highlighting at the same time the role of mercenaries,” he said. “Mercenaries are mentioned in our evidence, but they are often hiding in plain sight.”

David Reich, a geneticist at Harvard whose lab generated the data, noted that their paper “suggests that Greeks minimized a role for mercenaries, potentially because they wanted to project an image of their homelands being defended by heroic Greek armies of citizens and the armored spearmen known as hoplites.” Presumably, armies staffed with commandos-for-hire would undermine this picture.

The tyrants who ruled Greek Sicilian cities in the Hellenic Age recruited soldiers of fortune for territorial expansion, and in some cases because those rulers were wildly unpopular with their citizenry and required bodyguards. “The recruitment of mercenaries even spurred the use of coinage in Sicily to pay them,” Dr. Reitsema said.

The Sicily of antiquity, rich in resources and strategically located, was home to both Greek and Carthaginian colonies, which for a long time coexisted amicably. But when Terillus, tyrant of Himera, was ousted by his own people in 483 B.C., he called on his Carthaginian allies to help him retake the city.

Three years later, the Carthaginian general Hamilcar Mago sailed from North Africa to Himera with an expeditionary force estimated by Herodotus at more than 300,000 strong. (Modern historians put the figure closer to 20,000.) But cavalry and foot soldiers from two neighboring Greek Sicilian city-states, Syracuse and Agrigento, came to Himera’s aid, and Hamilcar’s troops were routed and his ships set ablaze. When all seemed lost, the general is said to have killed himself by leaping into a pyre.

In 409 B.C., Hamilcar’s grandson, Hannibal Mago, returned to settle scores. This time, the Greek army consisted mainly of citizens of Himera, with few reinforcements. The Greeks were defeated, and the city was razed.