Some of these satrapies hated being part of the empire (e.g. Egypt welcomed Alexander as their liberator from the Persian Empire), and all of them were inclined to rebel when the Emperor was weak or in difficulty.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.
