The Aetolian and Achaean Leagues held prominent positions of power in Hellenistic Greece. Why did the cities/peoples of these areas feel the need to “federalize” into larger alliance structures? What function did they serve? How was each league structured, and how did these structures differ?
Even though, I do not know enough about this era to write an answer this question deserves I'm merely using this comment to page the following users: /u/Daeres, /u/XenophonTheAthenian, /u/Giesskane, /u/Iphikrates. As they are all flaired in Greek History from the ancient eras to I believe (?) to the era you're asking about, so hopefully they can help you out. :)