Upon Philip's return, he dispatched Alexander with a small force to subdue revolts in southern Thrace. Campaigning against the Greek city of Perinthus, Alexander is reported to have saved his father's life. Meanwhile, the city of Amphissa began to work lands that were sacred to Apollo near Delphi, a sacrilege that gave Philip the opportunity to further intervene in Greek affairs. Still occupied in Thrace, he ordered Alexander to muster an army for a campaign in southern Greece. Concerned that other Greek states might intervene, Alexander made it look as though he was preparing to attack Illyria instead. During this turmoil, the Illyrians invaded Macedonia, only to be repelled by Alexander.