1. Establishment of the Koinon

In the historical era, the region of Ionia was divided among the cities forming the Koinon of Ionians or Panionium. The Koinon was a type of religious union centred around the cult of Poseidon of Helicon, originating in Boeotia. Its members held a joint festival at Panionium of Mycale.¹ The festival presumably became important after the 7th century BC, as there is no reference to it in the Homeric hymns, although the Iliad mentions the cult of Poseidon of Helicon.²

The Koinon consisted of 12 city-members (Ionian Dodecapolis), whose citizens identified themselves as Ionians. Two of the Koinon members were the Aegean islands of Samos and Chios, while the remaining ten cities (Miletus, Myus, Priene, Ephesus, Colophon, Lebedus, Teos, Clazomenae, Erythrae and Phocaea) were located on the western coast of Asia Minor. According to Herodotus and Pausanias, the number of the cities must have been fixed by the early 7th century BC. Pausanias reports that Smyrna was an Ionian city in the 23rd Olympic Games (688 BC).³ This must be connected with the capture of Smyrna by the Colophonians around that time, when the city was under Aeolian control. Herodotus says that Smyrna was the only Ionian city not accepted in the Koinon,⁴ probably because it allegedly depended on Colophon. Likewise, Magnesia ad Μaeandrum never became a member of the Koinon, as it was considered Aeolian, while Miletus assumed command of its territory after the city was destroyed by the Cimmerians.⁵

Some of the member cities were not of Ionian origin; others did not belong to the Koinon from its inception but were included later. The cities which probably constituted the original core of the Koinon were Miletus, Myus, Priene, Ephesus, Colophon, Lebedus and Teos. Chios was originally an Aeolian settlement; Phocaea was not admitted until it received Codrid kings from Erythrae and Teos (descendants of Neleus and Androcles, sons of Codrus, King of Athens, who, according to tradition, founded Miletus and Ephesus); Clazomenae was a colony of Colophon; the Ionian settlement at Erythrae dates after the Ionian migration; finally, Samos, according to some, was compelled to participate in the Koinon.⁶

2. The War of Melia

The shrine of Panionium was located in the ancient city of Melia (or Mele or Melite). According to the sources, Melia was one of the original 13 cities of the Koinon and was destroyed by the other 12 cities shortly before the raid of the Cimmerians under Lygdamis, around 650 BC. The region of Melia – likewise Pygela, Marathesium, Anaia and Thebes in Mycale– was divided among the rest of the cities. Although the historicity of the war has been disputed, it has been suggested that the Koinon and the joint festival at Panionium arose as a consequence of the joint war against Melia. The incorporation of the northern Ionian cities into the Koinon possibly took place after the end of the aforementioned war, while the destruction of the weakest Ionian cities and the annexation of the coast to the cities of the Koinon must have been completed in the first half of the 7th century BC, when Panionium was established.⁷

The theory suggesting a religious centre at Panionium already from the early 7th c. BC is not supported by archaeological findings - an altar and some surface finds on the top of the Panionium hill –, all later than the 7th c. BC.⁸ Moreover, according to an inscription from Priene, the war against Melia was an affair of only a few cities, aiming at territorial expansion, since, after its end, Ephesus, Priene, Samos, Miletus and possibly Colophon extended their boundaries. Besides, the view that it was a war organised by the Koinon cannot be accepted, since the source of the relevant information is Maeandrius of Miletus, a pseudo-historiographer .⁹

3. Operation of the Koinon

In archaic times, the cities participating in the Koinon were autonomous. According to some scholars, this was not always the case: the original Koinon was the relic of a semi-feudal kingdom under an Ionian king based at Panionium.¹⁰ Although an inscription of the Roman period refers to a ‘King of the Ionians’, there are no further data to confirm the validity of such assumptions.¹¹

The Koinon of Ionians was neither a confederacy with a rigid central authority, entitled to imposing resolutions to its members, nor was it subject to the control of a particular city. Herodotus says that in times of crisis –as it happened after Persian conquest of the Lydian kingdom (545 BC), when Bias of Priene unsuccessfully suggested that the citizens massively migrate to Sardinia, or at the beginning of the Ionian Revolt (499-494 BC)– the cities assembled at the shrine.¹² This created the impression that the 12 cities were members of an organised Koinon. Nevertheless, the problem with Herodotus is that the historian uses the exact same terms when he refers to the Dorian cities of the southeastern Aegean, despite the fact that no such information exists, that they ever formed a confederacy.¹³

Based on Herodotus' description, a hypothesis has been put forth that the structure of the Koinon allowed for unscheduled meetings at Panionium with the participation of representatives from all city-members. This presupposes the existence of some system of representation and an authority responsible for holding these meetings.¹⁴ It is not clear whether the representatives in these unscheduled meetings were the regular representatives of the cities in the Panionian festival or different representatives were elected each time. The former assumption seems more plausible, judging by the campaign to Cyprus in 497 BC, when the body of the ‘probouloi’, who decided on the participation, did not consist of army officers, as it might have been expected on the occasion. It may be assumed that in the regular meetings the probouloi dealt with issues concerning the festival, and military or political issues were part of the agenda only in case the Ionian cities were at stake. The political activities of the Koinon were restricted mostly to military operations, while the decisions of the unscheduled meetings were of diplomatic or military character. Such were the following: the decision to ask for Spartan help against the Persians (546 BC); the decision to send ships to Cyprus (497 BC); and the decision to participate in the naval battle at Lade (494 BC).¹⁵ Nevertheless, the city-members were not under the obligation to participate in military campaigns, if they believed their own safety was not at stake, as was the case with Miletus, Samos and Chios: they did not join the resistance against Cyrus, due to the fact that each of them had made a pact with him. The military operations were not launched under a common leader; the generals of the armed forces of each city jointly decided on the war tactics, like, for instance, on Cyprus and at Lade.¹⁶

The common belief of the Ionians that they formed an ethnic unity was expressed through the religious sentiment prominent at the Panionian festival. Only when the freedom of the Ionian cities was threatened originally by the Lydians and later by the Persians, did the Koinon start to evolve into a type of political organisation, although the city-members did not conclude to a common course of action against the enemy. It was probably for this reason that the Persians did not abolish the Koinon after the capture of the cities. However, in the early 5th c. BC, the Koinon achieved the kind of organisation which enabled it to lead the cities of western Asia Minor to the rebellion against the Persians.¹⁷

The Koinon was abolished after the unsuccessful Ionian Revolt. There is no information suggesting that it was reestablished or that the Panionian festival was held in Mycale in the 5th c. BC, when the Ionian cities were members of the Delian League. The Koinon was reestablished around 400 BC for a short period, when the Ionian cities asserted their independence against Persia with the help of Sparta. The Panionian festival was first celebrated in Ephesus most probably, because the city was the centre of the Spartan operations against the Persian king. Around 370 BC, with the commencement of the construction of the new city of Priene and the reestablishment of the old Koinon at Panionium, the festival returned from Ephesus to Mycale.¹⁸

The Koinon of Ionians regained its previous prestige after Alexander the Great declared the autonomy of the Ionian cities. The number of city-members rose to 13, when the newly built Smyrna joined the union. The Koinon retained its highly religious nature and held the Alexandrian festival in honour of the Macedonian king’s birthday. The celebration was originally held successively by all member cities, before the selection of a spot on the isthmus connecting the mainland to the peninsula of Erythrae.¹⁹

The importance of the Panionian festival and the cult of Poseidon of Helicon must have been overshadowed by the Alexandrian festival in the Hellenistic period. However, the Ionians continued to celebrated the Panionian festival in Mycale in honour of Poseidon of Helicon until the Roman years. According to Hellenistic inscriptions found in Priene and Strabo, a geographer of the Roman period, the priests of the Panionian festival came from Priene.²⁰