The district had belonged to a Thracian tribe, the Bottiaeans, in whose possession the town of Olynthus remained till 479 BC In that year the Persian general Artabazus, on his return from escorting Xerxes to the Hellespont, suspecting that a revolt from the Great King was meditated, slew the inhabitants and handed the town over to a fresh population, consisting of Greeks from the neighboring region of Chalcidice (Herod viii. 127). Olynthus thus became a Greek polis, but it remained insignificant (in the quota-lists of the Delian League it appears as paying on the average 2 talents, as compared with 9 paid by Scione, 8 by Mende, 6 by Torone) until the synoecism (i~rvvoiKwubs), effected in 432 through the influence of King Perdiccas of Macedon, as the result of which the inhabitants of a number of petty Chalcidian towns in the neighborhood were added to its population(Thucyd i. 58).
Henceforward it ranks as the chief Hellenic city west of the Strymon. It had been enrolled as a member of the Delian League in the early days of the league, but it revolted from Athens at the time of its synoecism, and was never again reduced. It formed a base for Brasidas during his expedition (424). In the 4th century it attained to great importance in the politics of the age as the head of the Chalcidic League (r~ KOLIbP Twi- XaX,ainiv). The league may probably be traced back to the period of the peace of Nicias (421), when we find the Chalcidians (ot ~ri OpcL,c~c XaXKu~4jc) taking diplomatic action in common, and enrolled as members of the Argive alliance.
There are coins of the league which can be dated with certainty as early as 405; one specimen may perhaps go back to 415-420. Unquestionably, then, the league originated before the end of the 5th century, and the motive for its formation is almost certainly to be found in the fear of Athenian attack. After the end of the Peloponnesian War the development of the league was rapid. About 390 we find it concluding an important treaty with Amyntas, king of Macedon (the father of Philip), and by 382 it had absorbed most of the Greek cities west of the Strymon, and had even got possession of Pella, the chief city in Macedonia (Xenophon, Hell. V. 2, 12).
In this year Sparta was induced by an embassy from Acanthus and Apollonia, which anticipated conquest by the league, to send an expedition against Olynthus. After three years of indecisive warfare Olynthus consented to dissolve the confederacy (379). It is clear, however, that the dissolution was little more than formal, as the Chalcidians (XaAiabi~c hirb Op~Kfls) appear, only a year or two later, among the members of the Athenian naval confederacy of 378377. Twenty years later, in the reign of Philip, the power of Olynthus is asserted by Demosthenes to have been much greater than before the Spartan expedition. The town itself at this period is spoken of as a city of the first rank (ir6)~is j-wpiavt5pos), and the league included thirty-two cities. When war broke out between Philip and Athens (357), Olynthus was at first in alliance with Philip. Subsequently, in alarm at the growth of his power, it concluded an alliance with Athens; but in spite of all the efforts of the latter state, and of its great orator Demosthenes, it fell before Philip, who razed it to the ground (348).
The history of the confederacy of Olynthus illustrates at once the strength and the weakness of that movement towards federation which is one of the most marked features of the later stages of Greek history. The strength of the movement is shown both by the duration and by the extent of the Chalcidic League. It lasted for something like seventy years; it survived defeat and temporary dissolution, and it embraced upwards of thirty cities. Yet, in the end, the centrifugal forces proved stronger than the centripetal; the sentiment of autonomy stronger than the sentiment of union. It is clear that Philips victory was mainly due to the spirit of dissidence within the league itself, just as the victory of Sparta had been (cf. Diod XVi. 53, 2 with Xen. Hell. V. 2, 24). The mere fact that Philip captured all the thirty-two towns without serious resistance is sufficient evidence of this. It is probable that the strength of the league was more seriously undermined by the policy of Athens than by the action of Sparta. The successes of Athens at the expense of Olynthus, shortly before Philip's accession, must have fatally divided the Greek interest north of the Aegean in the struggle with Macedon.
The chief passages in ancient literature are the Olynthiac Orations of Demosthenes, and Xenophon, Hell. v. 2. See EA Freeman, History of Federal Government, ch. iv.; AHJ Greenidge, Handbook of Greek Constitutional History (1896), p. 228; BV Head, Historia Numorum, pp. 184-186; G Gilbert, Griechische Staatsaltertkmer, vol. ii. pp. 197-198.
The view taken by all these authorities as to the date of the formation of the Confederacy of Olynthus differs widely from that put forward above. Freeman and Greenidge suppose the league to have originated in 382, Head in 392, Hicks (Manual of Greek Inscriptions, No. 74) before 390. The decisive test is the numismatic one. There are coins of the league in the British Museum which are earlier than 400, and one in the possession of Professor Oman, of Oxford, which he and Mr Head are disposed to think may be as early as 415-420.
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