For some of this information I must thank the inestimable Dr. Roel Konijnendijk, known on reddit as
u/Iphikrates. They remain an amazing source of information provided prolifically, eloquently, and freely, on a modern and evolving view on classical Greek warfare.
I would also like to say that I think this is an important subject worth discussing. You can consider this my "word of God" and ignore everything else, especially anything that contradicts this, because some of my statements were too blanket, delivered from a phone, or, I felt, not correct, after some thought.
What are Mercenaries?
Before we talk about mercenaries we need to discuss what mercenaries are. Mercenaries evolved into the system that we imagine in popular culture only over time as the system became more professional. In the archaic period, mercenaries were often not really mercenaries in the modern sense of transnational soldiers for hire, but rather the paid friends and network of wealthy aristocrats who could be pulled into assisting them in a coup of the city, or some military action. They did not have a significant or notable involvement in Greek history until the classical period, when they emerge as the primary force of the tyrants of Sicily, Gelo and Hiero, but how 'mercenary' these mercenaries really were is something we'll talk about. Mercenaries, whether from Thrace or parts of Greece, first emerge as aides to Greek hoplites in the area where many Mainland Greeks were weak, such as in skirmishing. We thus hear of Rhodean Slingers or Thracian Peltasts. Later, however, the growing number of mercenaries, the professionalization of the system as a consequence, and the growing use of mercenaries by Greeks eventually means mercenaries becoming the primary force of the
polis, before Makedon puts an end to the
polis as the dominant system of government among Greeks altogether and the successors in the east make extensive use of "mercenaries" (quotations needed as we'll get into).
Now let's separate this into some different types of "mercenary" to make a discussion about it simpler.
1.
Specialized Bands. These are the "Kretan Archers" or "Rhodean Slingers" of Total War fame. Specialized bands of mercenaries, usually only a few hundred strong, were either recruited with an existing command structure in place, or as individual units recruited at the point of origin until there were enough to meet the amount the city needed. These bands might be of a non-Greek origin, or from around the Greek World. There is nothing particularly geographically determined about these bands, nor should we think of them as "elite", but merely those skilled in their area of warfare and willing to serve as mercenaries. Dr. Konijnendijk gives the example of how the Akarnanians (in central Greece) were seen as better slingers than the Balareans, but the Balareans were more famed; in part because they were simply more available. Think of it like a product. It doesn't matter if an Italian pizza tastes better than the best pizza in your city, because you only have a choice between the pizza places which you can access. Specialized bands were used to provide a quality edge to some area in which a
polis was deficient during a war, and usually just hired for the duration of that war. These bands are useful, but it's easy to think too mechanically and assume they represent elites which Eretria cannot get. The Iapygians were famed for their skirmishers and light cavalry and that was what they were good at, and so Eretria already has this resource at home, and all without spending any money.
2.
Mercenary Armies. Mercenaries have several advantages over citizen soldiers, even for a democracy like 4th century BCE Athenai. First of all, they don't care about the agricultural cycle because they're not farmers, so they can fight year-round. Second, their deaths do not impact the population of citizens. Third, given that we are talking about citizen militias here, mercenaries could often be just be better at warfare. This is not always the case; see, how, for example, the Romans were able to fight armies composed of professionals and succeed victorious, but the Romans also had vast reserves of manpower to cushion losses and an explicitly martial culture. Many smaller
poleis did not necessarily have this culture, and as their citizens fought less and less it became harder to preserve what they had, or like Sparta their citizen army was so mauled that they never recovered. Carthage is the end-state of this mentality; Carthage remained a republic to the very end, though generals like Hannibal had wildly inappropriate amounts of power abroad, but aside from a sacred band of citizens at its core, the officers, and the cavalry, the Carthaginian army was an army composed of allies (such as north-african tributaries and Phoenician dependencies) and mercenaries. Carthage had a rather ingenious level of infrastructure, using its western Mediterranean maritime network to station recruits across the coasts of Spain, Africa, and Gaul, recruiting mercenaries from a vast pool.
3.
State Mercenaries. This is really a more complicated issue. Gelo's "mercenaries" were given land and territory. I am not sure they were from outside of Sicily at all, rather than being allies and opportunistic Sikeliote freemen who joined Gelo and Hiero in their quest for honor and glory. In that sense, how much are these mercenaries and how much are they professional soldiers? I think there's something to be said for the fact that that they were a force in opposition to the subjugated citizenry of Sicily which was opposed to Gelo and Hiero, and later to Dionysius I and II. If they were professional soldiers then this effectively made the tyranny of these rulers a kind of military dictatorship or kingdom similar to that of the
Diadokhi, who employed similar tactics, settling Macedonian veterans to become the farmer-soldier levy of their empires in the east. They're not quite professional soldiers, in that they weren't strongly tied to a single state (indeed, they were a valuable resource for the Diadokhi to compete over), but neither were they simply transient soldiers of fortune. Calling them state mercenaries seems to be the best; they're tied heavily to the success and support of rulers, but neither are they really just random foreigners, but rather deliberately settled and cultivated soldiers who became the basis of the state.
What are the Issues?
Well, that all sounds great. What's the issue with using mercenaries, then, in a general sense (NOT why Eretria won't use them, but their general drawbacks).
1. Cost. The most obvious reason why is expense. Through the 4th century BCE Greek cities just became far better at taxation and the collection of revenue. Athenai collected as much from internal revenue in the 4th century BCE as it did from its entire Empire in the previous century. Wealthier cities with larger coffers could fund mercenaries, but if they didn't have this kind of money hiring mercenaries was impossible. The most amazing example of this was when the region of Phokis, under sanction by the powers of Hellas for encroaching on the territory of Delphoi, home of the famed Oracle of Delphi, went absolutely sicko mode. They raided the sacred treasury of Delphi, seized 10,000 talents, and then proceeded to prosecute a massive war against the entire rest of Hellas they did not lose until Philip II of Makedon finally put them down. Yes, that Philip. But this also reflects how mercenaries can be extremely expensive as much as they can allow truly incredible feats of resistance against superior foes, and outside of extraordinary cases, mercenaries will be mostly the province of larger, richer states, with Carthage as the most obvious.
2.
Unreliability. This is far less memetic than is imagined in things like A Song of Ice and Fire. While it is true that there are cases where mercenaries would turn around and betray their master, this is generally because they weren't paying them, which is frankly fair enough. It's a bit of a dick move to import a Thracian peltast from across the sea and then not pay them a fair wage. The problem is precisely in the term
unreliable. You cannot
rely on mercenaries. You can
use mercenaries, and use them
well, but when you are in an emergency and have run out of money, they will turn against you. There are also cases where mercenaries have been flipped by the enemy offering better pay, but these seem more like isolated intrigues, usually of garrisons, rather than of an entire army. Still, if you don't pay them, they will fuck you up, either by going off and conquering some territory for themselves, pilaging your countryside, or
starting a massive civil war. Mercenaries by themselves may not end your state, but the disruption caused by them turning against you has a better chance of doing so.
3.
Political Disruption. The problem for a citizenry posed by mercenaries follows a little like this. When an army is composed of citizens, it is loyal to the citizenry. When an army is composed of mercenaries, it is loyal to their paymaster. Now, this is not an inevitability. A number of cities were capable of maintaining mercenaries throughout the 4th century BCE without ever facing a coup from them. However, this required smart political management and consistent funding. In a situation where there was real desperation such as Syrakousai in the face of the Carthaginians near the end of the 5th century BCE, the danger emerges. Dionysius I's rise to power is instructive. In the face of Carthage he gained considerable political power. Then he staged an attack on his life and requested a guard of 600 mercenaries, which was then increased to 1000. Mercenaries were the most obvious source of protection: If you were under attack from citizens, could you trust citizens to defend you, and this must have made enough sense to the democratic citizen body (in a time of extreme fear) that they allowed it. Much like in a modern army coup, the mercenary leader exploits the
unstable political situation, not the stable one. But this does not mean that the city would fallen to disorder anyway; it was a combination of the availability of mercenaries and instability that created this situation, just as a combination of popular military leaders after a revolution and an unstable political situation can easily combine into a dictatorship.
4.
Peacetime Banditry. The problem with mercenaries is that this is a somewhat transient group of men who are used to a professional wage equivalent to that of a skilled worker, which is really what they are. However, when an area has a lot of mercenaries, and those mercenaries aren't patronized by a state, as they were not in Hellas, and it's peacetime, things start to get unpleasant. Mercenaries, finding themselves without skills at home and having effectively become professional soldiers without a war to fight, may turn instead to banditry and begin ravaging the countryside until they are dispatched, or in the most radical cases attempt to carve out some territory for themselves if they are ethnically distinct or very well organized.
You'll notice that many of these issues pertain to mercenary types 2 and 3, and not so much to one. This is obviously because with smaller number of mercenaries you're not going to get them becoming powerful enough to challenge the state, but all of these issues could be repeated on a smaller level depending on how you handle mercenaries and their pay.
Why is Eretria anti-Mercenary?
1.
Suspicion of Mercenaries. Although Eretria has a number of allies and tributaries that it fundamentally relies on, these are often seen in familial or subordinate terms. They are trusted by Eretria because their relationship to it is long-established, with the most obvious inspiration being Rome's allies. Rome is also notable for never using mercenaries for most of the Republic and then exploding when it started using professional soldiers in conjunction with a dysfunctional political system. By comparison to allies, mercenaries are an unknown foreign element in Eretria whose allegiance to the city is temporary, and they are professional in a way neither the
Hieros Ekdromoi or
Kleos Exoria technically are since while both receive room, board, and lodging, when the city is not at war they're integrated into city life, not wandering off to go fight another war. In the city of stones everything is meant to build on the thing that came before, but mercenaries are transient and always moving from place to place looking for work; they don't represent a permanent addition to the city's arsenal but rather a temporary drain on its finances. Further, since the city has an ideal of the citizen soldier, there's an understandable dislike of them. However, this dislike was present across most of Hellas, and yet mercenaries were still used. So why not in Eretria?
2. Lack of Necessity. Eretria doesn't really need supplemental mercenaries. It outnumbered Taras by a huge amount in skirmishers and cavalry with the assistance of its allies. Through its allies, Eretria really and very easily removes the deficiencies it has in light cavalry and skirmishers, and the Iapygians were known as cavalry and skirmishers, and so it's not as if the city is starving for quality. Also through its allies it adds another 25% strength to its hoplite forces. Eretria hasn't fought many wars that would require mercenaries or have pushed its current military system to the brink; it revealed some issues in the quality of its Hoplites that the Antipatrids wanted to address. But that isn't really enough to start draining the city's coffers. As a city, Eretria is constantly attempting to re-invest money into itself as much as possible, and recruiting mercenaries without the need, or at the expense of using costless allies, would be deeply scrutinized. The other major reason is...
3. Political Opposition. The
Kleos Exoria and
Hieros Ekdromoi are made out of a particularly Eretrian ideal of martial culture. The city has faced few hardships to show the necessity to them that mercenaries can assist the city. The city has never been defeated by mercenaries, and in fact the
Kleos Exoria have their origin in beating mercenaries as mercenaries; they are, in effect, even
better than mercenaries, as they would argue. Without facing massive losses or being defeated in some battle or another, there is no reason for these two pillars of Eretrian martial culture to concede symbolic ground to the presence of professional soldiers in Eretria's employ in the same areas as them, nor should they, because there is no reason to. Eretria has never needed mercenaries and will never need mercenaries, until it does. And when it does get to that point, the city will prefer settling them as citizens in faraway colonies because...
4. Eretria is no ordinary state. The city has a history of assimilating those around it into permanent or near-permanent allies and agglomerating friends at a disturbing rate. It is also fundamentally a state of immigrants in a very peculiar kind of manner in which the city's continued survival is dependent on rapid immigration. If the city is in a situation where it feels as though mercenaries are necessary, even in a situation where they are on the frontline with the city's hoplites or assisting the cavalry, the city will try and figure out some way to transform those mercenaries into permanent allies because they're a major military asset that can be useful. A legion of farmer-soldiers to be called from around the Adriatic to come to their patron's defense is a useful group, and by committing them to various
poleis rather than to a ruler or a dynasty they become integrated back into normal politics rather than serving as a threat to the city forever.
So all of this is to say that the city will be open to recruiting mercenaries when it is necessary, in circumstances when it feels it is necessary, in a reasonable way that it does not feel endangers the body politic and binds those mercenaries to the city. If there are reasons to recruit mercenaries, characters will consider those reasons and potentially open it up to the assembly to choose whether to recruit them. Until that point, the discussion of mercenaries remains an unnecessary diversion which has gotten too hostile. So let this be the last word and reference on the subject, and let us move onto to other topics that don't inspire such ill-will.
I will not accept any further dispute or complaint on this issue. I have said my piece.
