It is unfortunate that the evidence for the Bithynian military dates almost entirely from the second century BC and later. The late fourth and third centuries BC were times of significant change in the armies of Asia Minor. The invasion of Alexander set about a drastic hellenization process which heavily influenced the militaries of all states on the periphery of the empire and which was to continue for some time into the third century. In addition to this, the introduction of the Galatians into Asia Minor had a large effect on the material culture of these armies.

One of our only glimpses of the Bithynian soldier of the third century is provided by the stele of Dionusios from Alexandria in Egypt. His is a type of funerary monument which was peculiar to the Hellenistic period - stelai decorated as they had been from the Classical period with architectural fixtures around a main field, but in that field there was instead of a sculpted relief a painting on the flat stone surface. These painted stelai, of which examples, all of them dating to the 3rd and 2nd centuries BC, have been found in Alexandria, Cyprus, Sidon, Demetrias in Macedonia, and the northern Black Sea. A large proportion of these stelai were for soldiers (the entirety of the stelai found at Sidon with surviving paint, around 17 in total, were for mercenary soldiers), and some paintings with paint still visible depicting up to three soldiers on a single stele have been found. Dionusios’ stele is one of these. Though he was a mercenary, there is little reason to believe that he would have changed his equipment or costume while serving abroad. Of the numerous other painted stelai depicting soldiers which have been found in and around the modern city of Alexandria, the mercenaries (who comprise almost all of them) are all armed in their respective national fashions. Dionusios wears a dark brown chiton with a single white stripe down the front of it, a pair of dark brown boots, and a laurel wreath on his head. He holds a medium length spear while his diminutive page holds two shorter javelins and his yellow-brown thureos (a large oval shield). The boy wears a short white chiton as well and an item of headgear painted in blue which most likely represents an iron helmet, seemingly of the pilos type.

It is notable that Dionusios is the only soldier depicted on the Alexandria stele to carry a thureos who is not a Galatian. It seems that the Hellenistic militaries that came into contact with the Galatians only began to adopt their style of armament towards the middle of the third century BC, and so Dionusios would have to date to the latter half of that century. This also fits in well with the accepted dates of most of the Alexandrian painted stelai which places them in the second half of the third century. Therefore, it is likely that by the turn of the century, the equipment of at least the Bithynian infantry had already undergone a significant reform. It was also about the middle of the third century when the use of shields became popular again with cavalry in the eastern Mediterranean, and so it was most likely around the end of that century that carrying shields also became fashionable among the Bithynian heavy cavalry.

Interestingly, the stelai featuring Thracian names are clustered throughout the countryside. Not a single Thracian name can be found in epigraphical evidence from within the poleis of Bithynia until the first century AD. The Thracian names that appear on numerous monuments dated to the Hellenistic period from the rural “heartland” of Bithynia around Nicaea and Prusa are all rural in provenance.

There could have been various reasons for this. Xenophon reported that in his day within Bithynia there were no cities but that there were many villages inhabited by the natives. These men may simply be descendants of these native Bithynians who remained on their ancestral estates through a variety of political upheavals. Alternatively, Antigonus Monophthalmus, who actively moulded the urban geography of Bithynia, may have done the same with the chora and settled soldiers (including Thracians) in this area; Lysimachus, who controlled large portions of Bithynia and Thrace, may have acted likewise. Another possibility is that the Bithynians actively copied the style of military settlement of soldiers in katoikai as practiced by the Seleucids in and around Asia Minor. At any rate, our knowledge of Bithynia in the late fourth and third centuries BC is insufficient to provide any further evidence, and so this is mere speculation.

Regardless of their origins, it seems, therefore, that despite the efforts of Nicomedes and his successors to hellenize Bithynia, the Bithynian aristocracy preferred to inhabit the rural towns which their ancestors had lived in for generations. It was only because of the autonomy of the Bithynian kingdom that this group of the native élite was able to own large estates – by the early Imperial period, the owners of large estates in the Bithynian countryside have Roman and Greek names, and not a single Thracian name can be found listed in positions of importance.

The armament, equipment, and costume of these cavalrymen appear to have been thoroughly hellenized, though with some subtle Celtic influences as well. The standard equipment seems to have been a cuirass (of the cavalrymen depicted on Bithynian funerary stelai, all but one wear the common “shoulder-yoke” cuirass), a helmet, a large circular shield, one or more spears, and a sword.

Almost all of the Bithynian cavalrymen are depicted wearing a style of helmet which was unique to the region around the Black Sea and Asia Minor from the late third century BC to the first century BC. This was a peculiar Hellenistic-style helmet which seems to have been a synthesis of the later Hellenistic Pilos type helmet with the Boeotian type. The wide, crimped brim of the Boeotian type, which allowed for maximum visibility while also shielding the eyes from the sun and deflecting downward blows, was combined with a unique highly arching bowl and peak of the late Pilos type. However, unlike other late Hellenistic Pilos type helmets, the bowl rises to a slender peak. This kind of helmet can be seen on Stelai A, B, and I, as well as on Stele M, that of Phokritos from Yalova, on which it is most clearly represented.

Stele N shows a cavalryman in a rather dramatic scene of combat. He is riding down a dying Galatian cavalryman whose horse rears backwards over another dead or dying horse. Though it is hard to ascertain details of the Bithynian horseman who is heavily effaced, the offset rim of his hoplon can be made out behind him. One other interesting aspect of this stele is that the Galatian is pierced by two javelins, perhaps indicating that the Bithynian cavalryman in this case wielded multiple javelins and not a single spear. Unfortunately, it is often hard to judge whether a vignette on a stele is self contained or not, something which can often complicate interpretations of the equipment on such battle scenes. If this stele is self contained, then the two javelins are the Bithynian rider's. However, if it is not, and the presence of another defeated cavalryman's horse could indicate so, then one or even both of the weapons piercing the vanquished could be from another warrior. Some other Bithynian and Mysian cavalrymen are depicted on funerary stelai carrying multiple javelins, but these cavalrymen appear unarmoured, and so are most likely light cavalrymen.

Of the stelai depicting cavalrymen, a few show men wearing no defensive armour and carrying only a few javelins with them. The clearest example is Stele F, Phila’s stele. The only sort of extra protection that Phila appears to wear is what appears to be some sort of jerkin or overtunic which the artisan has taken care to show as being much more rippled than his undertunic which extends down to his mid-thigh.

Identically-equipped cavalrymen can be found on numerous Mysian stelai. Similar Thracian cavalrymen are depicted on some stelai decorated with scenes in relief from Byzantium dating to the second century BC as well. Those stelai, however, seem to have more in common with other Thracian stelai than Bithynian stelai in that they usually only have a single scene in the central field, rather than the multiple, often multi-layered registers seen on almost all Bithynian stelai. This could be a sign of Thracian mercenaries serving in the Bithynian army adopting local funerary customs, but it seems more likely that these are Bithynian citizens. Many of these stelai are also fairly large and well-crafted, indicating that their owners at least came from a wealthy family, if they weren’t wealthy themselves. If they indeed are native Bithynians, this is yet another sign that wealthier citizens able to afford well-crafted tombstones served in the lighter and typically poorer elements of the army.

The stele of Diliporis (Stele C) is quite a remarkable piece when considered both within the context of the Bithynian stelai and within the corpus of Hellenistic funerary stelai at large. The stele was made for Diliporis who was evidently the head of a large Bithynian family. He sits with his wife Dintise and his two daughters in the upper register and on the wall behind them hang several weapons with armour. To the left the head of a horse can be seen with a groom; to the right of this is a fairly small round, rimless shield with two short spears behind it, and to the right of that is a helmet with a decorated visor, an offset rim, cheek pieces, and surmounted by a peak. On the far right hangs a thureos with a trilobate sword behind it.

In the register below this, the male members of the family are arrayed for the viewer. On the far right stands Numisios who is fully armed. He carries the round, rimless shield and two short spears, most likely the same spears and shield seen hung on the wall on the left of the upper register, and wears a helmet, with a plume, similar to the one shown hanging on the right. He also wears a cuirass, the form of which cannot be determined with accuracy but which is probably a linothorax with pteruges (textile strips protecting the thighs and shoulders) and a sword on his left hip. He also wears high boots that reach up about halfway to his knees. To his left stands Mokasis, who wears the chiton and chlamus of a military man and a sword on his left. Next in the lineup is Zardoiles, who carries a very large thureos and also wears a linothorax and some sort of helmet, evidently the one seen in the upper register. The hilt of a sword can be seen on his left side. The name of the next figure is no longer preserved; he wears a large ephaptis and carries what appear to be scrolls, probably marking him as a scholar or student. The final figure is a cavalryman whose name is also no longer preserved. He wears a plumed helmet that appears similar to Numisios’ (and those of many other cavalrymen on the other stelai) and he wears a cuirass with an officer’s sash. The most remarkable aspect of this stele is Numisios. His panoply is clearly represented, seemingly completely, and it is unlike that of any other soldier depicted in the art of the Hellenistic period.

Asclepiodotus, in his first century BC treatise on tactics entitled Techne Taktike, divides the infantry into three divisions: phalangites (“hoplites of the phalanx”), light troops or psiloi, and an intermediate category of infantry called peltasts. This division of elements of the army into threes is repeated in all other elements of the army as described by Asclepiodotus, and it seems a highly artificial division that probably has its roots in rhetorical teaching. He also seems to omit, ignore, or shoehorn into other divisions several distinct types of troops (such as the thureophoroi, who had been ubiquitous in the Hellenistic militaries from the middle of the third century BC, and who fit neither in the psiloi nor in the peltastai) which calls into question his actual knowledge of Hellenistic militaries. However, the prominence of the peltastai within his division begs the question of what exactly these troops were. It should be noted that these are unrelated to the “Classical” and much more common use of the term peltast, which was to describe true light troops armed with similarly-sized shields but otherwise entirely unrelated. Asclepiodotus writes that:

The corps of the peltasts stands in a sense between these two [i.e. the phalangites and the psiloi], for the pelte is a kind of small, light shield, and their spears are much shorter than those of the hoplites.

His description implies that they were not unlike the phalangites in other ways, and so would have worn cuirasses and greaves. Considering that he describes the shields of the phalangites, who he says are “protected by shields of the largest size,” as being eight palms (about 60 centimeters) in diameter, these peltai must have been fairly small. The description of the shorter spears simply indicates that these men were not equipped with the sarissai of the phalangites, but instead with shorter fighting spears (dorata).

The family of Diliporis is clearly a family of Bithynian citizens - all of the preserved names are Thracian in origin - and very wealthy ones at that, as Diliporis’ wife and children could afford to buy an exceptionally large and well-crafted funerary stele for him. Yet we see that one son is a cavalryman, another is a thureophoros, and yet another is a peltast. The immediate conclusion to draw from this is that Bithynian citizens served not just as citizen cavalry but also as thureophoroi and peltasts within the Bithynian army. This is borne out by the stele of Mokazis (Stele A) and another anonymous stele showing part of a battle scene (Stele B). The former shows Mokazis with two sons, a thureophoros and a spear bearer, and the latter shows the deceased’s son wearing a helmet and carrying a large round shield and a sword.