The Lost Army of Cambyses was, according to an ancient legend, a formation of 50,000 Persian soldiers that disappeared in the Western Desert of Egypt in 524 BC after becoming engulfed in a sandstorm. They had supposedly been sent by Cambyses II in order to subjugate the Oracle of Amun at the Siwa Oasis. Around this time, Cambyses, who had succeeded Cyrus the Great as monarch, was leading the first Achaemenid conquest of Egypt.