The 4th century saw the greatest prosperity of the Bosporan Kingdom with the barbarian threat fading away significantly and the Spartokid dynasty gaining Nymphaion and Theodosia, as well as the land of neighboring barbarian tribes. Inscriptions are virtually the only source also for establishing the nature of the relations between the Bosporan kingdom and the rest of Hellenic oikumene. Next to official decrees, funerary inscriptions play a substantial role in this description. In this context the Spartokid kings come through as the biggest exporters on the grain market of the age. The pan-Hellenic character of this trade is illustrated well by an excerpt from Demosthenes’ speech against Lakritos. Trading with the Bosporus and Olbia is in the hands of the Athenians, but merchants from Phaselis, Eubea and Halikarnassus are also involved. Wine is taken to the Bosporus and grain is carried on the way back. The archaeological record in the form of pottery containers and especially amphora stamps has produced substantial proof of this commerce. The predominant products (counted in the thousands) in the 4th and 3rd century BC are containers from Sinope This concentration suggests especially intensive contacts between the Bosporan Kingdom and Sinope, Heraklea and other towns on the southern Black Sea shore. The epigraphic material confirms this assumption; suffice it to look at the stone epitaphs of citizens of Sinope After the fall of Athens and the appearance of Ptolemaic competition on the grain market, these contacts took on particular importance. An epigraphically attested presence of citizens of Sinope From the historical point of view this reflects the loss of influence, also in the cultural sphere, by Miletus and speaking more broadly, Ionia. Athenian influence in the 5th century must have been very strong due to the role of Athens as a center of art and culture, and its political domination. Athenian influence is also observable in the language in the form of Atticisms present in some of the inscriptions from the period as well as examples of the use of the stoichedon. Athenian domination lasted for a relatively brief period of time, but it was sufficient to cause a gradual disappearance from the language of the Bosporan and Black Sea Greeks of both Ionisms and Doricisms. The beginnings of the Pontic dialect can perhaps be placed in this period. While it is possible to trace the language evolution, there is no indisputable evidence to prove how the newest cultural trends, including literary ones, reached the Cimmerian Bosporus in the 4th century BC. The few preserved inscriptions mentioning citizens of Sinope At the same time Miletus regained at least some of its old energy after the Persians succumbed to Alexander and attempted to renew ties with its old colonies. This appears to have had little to do with the Bosporan Kingdom or at least it fails to have been reflected in the inscriptions. Even so, the world situation in general was not conducive to any Black Sea state or city independently defending its interests in confrontation with the greatest Hellenistic monarchies. This was particularly evident in the western part of the region, but the Bosporan Kingdom must have faced similar problems despite its greater power and remoteness. This greater independence appears to be borne out by the Bosporan King Eumelos accepting 1000 refugees from the city of Kallatis besieged in 310/9 BC by Lysimachos and not only taking them in, but also granting them land to establish a new town. It is one of the few historical events concerning the Bosporan Kingdom that have found mention in the literary sources. According to Diodorus, Eumelos enlarged considerably the territory under his rule at the cost of the barbarian tribes and gained Greek approval by taking measures against the Caucasian pirates and euergesis with regard to the poleis. The effort to unite the Pontic Greeks failed with the death of the king within just five years of taking the throne.
The archaeological and epigraphic data combined led Vinogradov to coin the term “Pontic cultural koine”. What he had in mind was that all the available sources indicated that in the Hellenistic period the Black Sea cities maintained the most intensive contacts among themselves. One of the crowning arguments in favor of this idea was the similarity of representations on funerary stelae and, following L. Robert, the lexical similarity of the language in official decrees. The truth of the matter is that these arguments have relatively little to do with the Bosporan Kingdom, although they can be made to refer to the region broadly understood.