Peloponnesian League
The next year, in 432 BC, Corinth and Athens argued over control of Potidaea (near modern-day Nea Potidaia), eventually leading to an Athenian siege of Potidaea. In 434–433 BC Athens issued the "Megarian Decrees", a series of decrees that placed economic sanctions on the Megarian people. The Peloponnesian League accused Athens of violating the Thirty Years Peace through all of the aforementioned actions, and, accordingly, Sparta formally declared war on Athens.