Cambyses II was an ancient Persian king who ruled from 530 to 522 BCE. He was the son of Cyrus the Great, the founder of the Achaemenid Empire. Cambyses is best known for his conquest of Egypt, which he successfully invaded in 525 BCE, expanding the empire significantly. His reign was marked by a focus on military campaigns and the consolidation of power. However, Cambyses faced challenges, including internal dissent and issues with governance. He died under mysterious circumstances, leading to a brief period of instability before the rise of Darius I, who would further expand the empire.