History affirms the fact that from the time of Thales. To the time of Aristotle, the Greeks were victims of internal disunion, on the one hand, whereas on the other, they lived in invariable fear of invasion from the Persians who were a general enemy to the city states.
As a result when they were not fighting with one another they found out themselves active fighting the Persians, who soon dominated them as well as became their masters. the region from the coast of Asia Minor to the Indus Valley became united under the solitary power of Persia, whose central territory Iran has lasted as a national unit to the present day. Persian expansion was similar to a nightmare to the Greeks who dreaded the Persians on account of their untouchable navy, and organized themselves into Leagues and Confederacies in order to resist their enemy(Bentley 565-580).
Apart from the confrontation of a common foe, the Persians, a study of the purpose of the Leagues, discloses the enmity and spirit of aggression which were attribute of the relationship which existed between the Greek city states themselves.
For that reason in 505 B.C., the Peloponnesian says signed treaties among themselves, pledging warfare against Sparta who had absorbed them under her power. Meanwhile, Aristogoras revived the Ionian League (499-494 B.C.) to resist Persian aggression, and friendship between Athens and Aegina was restored by the Hellenic League (481 B.C.) which was afterward converted into the Confederacy of Delos (478 B.C.) as mentioned elsewhere(Bentley 565-580). In like manner, Thebes also fell in line with the general temper of the age and organized the Boeotian League, a federation of city states, for self-protection and aggression.
In 377 B.C. a second Athenian Confederacy was organized, but this was to frustrate the aims of the Lacedaemonians and to compel them to respect the right of the Athenians and their allies. Likewise in 290 B C., the Aetolian League, made up of the States of central Greece, gained control of Delphi, and frequently violated Achaean rights in the Peloponnesus, while in 225 B.C. Antigonus Doson organized another Hellenic League, with the purpose of obstructing the ambitions of Sparta and her Aetolian allies.
Owing to the ambitions of Athens to dominate the Ionians and other neighboring peoples, Pericles launched a campaign of alliances and conquests extending from Thessaly to Argos, and from Euboea to Naupactus, Achaea and the chief islands of the ...