After the conquest of Babylon by the Persian Empire, Cyrus the Great allowed the Jews to return to their native land and rebuild Jerusalem, sacked by Nebuchadnezzar II in 586 BC. While rebuilding the city's fortifications, the Persian administration also constructed a new citadel north of the Temple Mount enclosure, as part of a general Persian effort to bolster the empire's defences. This citadel is the Biryah (Hebrew: בירה) referred to in , appearing as the Baris in Greek translations of the Septuagint. The origin of the word is not entirely clear, but may have been borrowed into Hebrew from Assyrian birtu or bistu meaning a citadel or castle within a city, or a fort located at a strategic position outside a city. It may also derive from the Old Persian baru, meaning 'fort'.