Perdiccas betrays the Athenians once again and sends one thousand troops to support a Spartan assault on Acarnania in 429 but they arrive too late to help (Thucydides 2.80).
In response to this, Sitalkes of the Thracian Odrysian state invades Macedonia with the promise of support from Athens.
This support never materializes, and Perdiccas once again uses diplomacy to ensure the survival of Macedonia.
He promises the hand of his sister in marriage to the nephew of Sitalkes, who then persuades Sitalkes to leave.