Daniel 6:1-2

When the Medo-Persian alliance overthrew the Neo-Babylonian Empire, it acquired much geographic territory that it proceeded to incorporate into its kingdom. The Persian Empire became the largest that the world had yet seen, eventually encompassing modern Turkey, Egypt, and parts of India and North Africa as well as Babylonia. Darius divided his realm into 120 satrapies or provinces, and set a satrap ("protector of the realm") in charge of each one (cf. Esther 1:1; Esther 8:9). They reported to three commissioners, one of whom was Daniel. Evidently Darius had heard about Daniel’s unique gifts and accomplishments as a Babylonian administrator, and wanted to use him in his cabinet. Daniel 6:1 strongly suggests that "Darius" and "Cyrus" refer to the same person. Because of the vast geographical region that 120 satrapies entailed, this number and size of provinces would be consistent with the Persian Empire as historically ruled by Cyrus.