Following this, Athens instructed Potidaea in the peninsula of Chalkidiki, a tributary ally of Athens but a colony of Corinth, to tear down its walls, send hostages to Athens, dismiss the Corinthian magistrates from office, and refuse the magistrates that the city would send in the future. The Corinthians, outraged by these actions, encouraged Potidaea to revolt and assured them that they would ally with them should they revolt from Athens. During the subsequent Battle of Potidaea, the Corinthians unofficially aided Potidaea by sneaking contingents of men into the besieged city to help defend it. This was a direct violation of the Thirty Years' Peace, which had (among other things) stipulated that the Delian League and the Peloponnesian League would respect each other's autonomy and internal affairs.