The people in said country become dissatisfied with their government and demand change. Either through protest, revolt, etc..
Checks and balances, principle of government under which separate branches are empowered to prevent actions by other branches and are induced to share power. Checks and balances are applied primarily in constitutional governments.
Answer:
The Persian Empire entered a period of decline after a failed invasion of Greece by Xerxes I in 480 BC. The costly defense of Persia's lands depleted the empire's funds, leading to heavier taxation among Persia's subjects