Second Athenian Empire

The Second Athenian Empire or Confederacy was a maritime confederation of Aegean city-states from 378–355 BC and headed by Athens, primarily for self-defense against the growth of Sparta and secondly, the Persian Empire.

Origins
The formation of the confederacy was stimulated by the invasion of Attica by Sphodrias of Sparta and Sparta's refusal to prosecute him for his actions (according to Xenophon and Diodorus Siculus). It was extremely popular at first, with a number of states previously controlled by Sparta signing up as members due to Sparta's increasing imperialism over the Decree of Aristoteles. An inscribed "prospectus" for the league was found at Athens (Inscriptions Greques 2, 43, also known as the Aristoteles decree) dating to 377 BC, detailing the aims of the new league. The intention was to ensure that Sparta would allow all the Greeks to be autonomous; the states involved were all to have autonomy; and Athens was not permitted to own land in any of the states who were members, or to inflict upon them a garrison or a cleruchy; each member could also choose their own constitution, not necessarily a democracy. This 'prospectus' appears to try to promise that this league would not turn out the same way as the earlier, 5th century BC Delian League which had been unpopular in many quarters as Athens' behaviour was heavy handed at times particularly towards those states which had rebelled or showed signs of wanting to rebel.

Running of the League
The League had a synedrion at Athens,within which each of the league's members were to be autonomous and have one vote each. Along with Athens this was a bicameral system and it is thought that Athens could not make any decisions without the agreement of the synedrion. There were to be no tributes as there had been in the 5th century Delian League, but there were "contributions", syntaxeis to be paid, these were probably not required every year but might have been requested during times of crisis.

Rise of Thebes
Sparta's interference and invasion of Thebes in 382 BC gave the latter a very good reason to join the league. However her behaviour within the league became difficult and Athens started to realise that Thebes was not necessarily to be trusted. For example, Thebes destroyed Plataea in 372 BC, which had only recently been refounded. Athens started to think about negotiating peace with Sparta; it was while Athens was discussing this with Sparta that Thebes defeated the Spartan army conclusively at Battle of Leuctra (371 BC).

Later history
After Sparta's defeat in 371 BC by Thebes, the original terms set out in the prospectus had been achieved, yet Athens did not want to give up her power over these states. A series of revolts ending with the Social War (357-355 BC) and the revolts of several of Athens' major allies finally put an end to the confederacy.