The Medo-Persian Empire, represented by the chest and arms of silver in King Nebuchadnezzar's vision, emerged as a significant power after Babylon. Cambyses I, son of Cyrus, played a crucial role in expanding this empire by overthrowing Egypt and Libya in 525 BC, contributing to the empire's vast territorial reach, nearly double the size of Babylon. Despite its impressive military and political might, the empire faced challenges with internal unity and succession struggles, though strong rulers like Cambyses helped maintain its integrity during its early years.