While the city was burning, the Lydians and all the Persians who were in the citadel, being hemmed in on every side since the fire was consuming the outer parts and having no exit from the city,
Hdt. 5.101 The Ionians burn Sardis to the ground 498 BCE The Achaemenid Empire is not indestructible. Even the Ionians (notorious servant folk) can be convinced to revolt.