Cyrus the Great and Darius the mede of Daniel 5?

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Daniel 5.31

Ver. 31. "And Darius the Median took the kingdom," This was Cyaxares the son of Astyages, and uncle of Cyrus; he is called the Median, to distinguish him from another Darius the Persian, that came after, (Ezra 4:5), the same took the kingdom of Babylon from Cyrus who conquered it; he took it with his consent, being the senior prince and his uncle. Darius reigned not long, but two years; and not alone, but Cyrus with him, though he is only mentioned. Xenophon says, that Cyrus, after he took Babylon, set out for Persia, and took Media on his way; and, saluting Cyaxares or Darius, said that there was a choice house and court for him in Babylon, where he might go and live as in his own:

"being about threescore and two years old"; and so was born in the eighth year of Nebuchadnezzar, the year in which Jechoniah was carried captive, (2 Kings 24:12), thus God in his counsels and providence took care that a deliverer of his people should be raised up and provided against the appointed time. Darius was older than Cyrus, as appears by several passages in Xenophon; in one place Cyaxares or Darius says,

"since I am present, and am 'elder' than Cyrus, it is fit that I should speak first;"

and in another place, Cyrus, writing to him, says,

"I give thee counsel, though I am the younger"

and by comparing this account of the age of Darius with a passage in Cicero, which gives the age of Cyrus, we learn how much older than he Darius was; for, out of the books of Dionysius the Persian, he relates, that Cyrus dreaming he saw the sun at his feet, which he three times endeavoured to catch and lay hold upon, but in vain, it sliding from him; this, the Magi said, portended that he should reign thirty years, and so he did; for he lived to be seventy years of age, and began to reign when he was forty; which, if reckoned from his reigning with his uncle, then he must be twenty two years younger; or if from the time of his being sole monarch, then the difference of age between them must be twenty four years; though it should be observed that those that make him to reign thirty years begin his reign from the time of his being appointed commander-in-chief of the Medes and Persians by Cyaxares, which was twenty three years before he reigned alone, which was but seven years; and this account makes but very little difference in their age; and indeed some have taken them to be one and the same, their descent, age, and succession in the Babylonian empire, agreeing.

(The New John Gill's Exposition of the Entire Bible)

Darius: the name of several kings of Media and Persia. Herodotus says that the name is equivalent to "the restrainer"; three kings bearing this name are mentioned in the OT.

Darius the Mede, "the son of Ahasuerus of the seed of the Medes," who succeeded to the Babylonian kingdom on the death of Belshazzar, being then sixty-two years old. Only one year of his reign is mentioned; but that was of great importance for the Jews. Daniel was advanced by the king to the highest dignity, probably in consequence of his former services; and after his miraculous deliverance, Darius issued a decree enjoining througout his dominions "reverence for the God of Daniel" (Dan 6:25).

The extreme obscurity of the Babylonian annals has given occasion to three different hypotheses as to the name under which Darius the Mede is known in history. The first of these, which identifies him with Darius Hystaspis, rests on no plausible evidence, and may be dismissed at once. The second, which was adopted by Josephus, and has been supported by many recent critics is more deserving of notice. According to this he was "the son and successor of Astyages," who is commonly regarded as the last king of Media. It is supposed that the reign of this Cyaxares has been neglected by historians from the fact that through his indolence and luxury he yielded the real exercise of power to his nephew Cyrus, who married his daughter, and so after his death received the crown by direct succession... Herodotus expressly states that "Astyages" was the last king of the Medes, that he was conquered by Cyrus, and that he died without leaving any male issue...A third identification remains, by which Darius is represented as the personal name of "Astyages," the last king of the Medes...The name "Astyages" was national and not personal, and Ahasuerus represents the name Cyaxares, borne by the father of "Astyages"...If, as seems most probable, Darius (Astyages) occupied the throne of Babylon as supreme sovereign with Nerigalsarassar as vassal-prince, after the murder of Evil-merodach (Belshazzar) BC 559, one year only remains for this Median supremacy before the victory of Cyrus BC 558, in exact accordance with the notices in Daniel and the apparent incompleteness of the political arrangements which Darius "purposed" to make (Dan 6:3).

Astyages, the last king of the Medes, BC 595-560, or BC 592-558. The name is identified...[as] "the biting snake," the emblem of the Median power.

Ahasuerus, the name of one Median and two Persian kings mentioned in the OT. It may be desirable to prefix to this... a chronological table of the Medo-Persian kings from Cyaxares to
Artaxerxes Longimanus, according to their ordinary classical names.

1. Cyaxares, king of Media, son of Phraortes, grandson of Deioces and conqueror of Nineveh, began to reign BC 634.

2. Astyages his son, last king of Media, BC 594.

3. Cyrus, son of his daughter Mandane and Cambyses, a Persian noble, first king of Persia, 559.

4. Cambyses his son, 529.

5. A Magian usurper, who personates Smerdis, the younger son of Cyrus, 521.

6. Darius Hystaspis, raised to the throne on the overthrow of the Magi, 521.

7. Xerxes, his son, 485.

8. Artaxerxes Longimanus (Macrocheir), his son, 465-495.

In Daniel 9:1, Ahasuerus is said to be the father of Darius the Mede. Now it is almost certain that Cyaxares is a form of Ahasuerus, grecized into Axares with the prefix Cy- or Kai-, common to the Kaianian dynasty of kings, with which may be compared Kai Khosroo, the Persian name of Cyrus. The son of this Cyaxares was Astyages, and it is no improbable conjecture that Darius the Mede wass Astyages, set over Babylon as viceroy by his grandson Cyrus, and allowed to live there in royal state.

(Dr. William Smith's Dictionary of the Bible, 1872)

Media: ancient country & province of Persian Empire SW Asia in NW modern Iran Persia: see Iran (Webster's)

Media, in ancient times the name of northwest Persia. The Medes
were an Aryan people like the Persians. Their state religion was Zoroastrianism, and the Magi its priests. (Universal Standard Encyclopedia)

Medes, Media, a people and country called by the same word, Madai -- in Hebrew and Assyrian... Among the Semitic peoples... the name of the Medes continued long to be more familiar than that of the Persians, partly by reason of their greater antiquity, and partly because the Medes formed the principal portion of the Iranian population. Hence the word is more frequent than 'Persia,' except in the later books of the OT. Madai is mentioned in Gen 10:2 among the sons of Japheth, with no allusion to the Persians. So the Medes and not the Persians are mentioned in prophecy as the prospective destroyers of Babylon (Isa 13:17; 21:2; Jer 25:25; 51:11).

(Hastings' Dictionary of the Bible)

Joel 1:4 describes four types of locusts:

1. palmerworm: cutting locust
2. locust: swarming locust
3. cankerworm: hopping locust
4. caterpillar: destroying locust

Jerome relates that the Hebrews interpreted the four as:

1. palmerworm - Assyrians, Babylonians, and Chaldeans
2. locust - Medes and Persians
3. cankerworm - Macedonians, and all the successors of Alexander; especially King Antiochus
4. caterpillar - Roman Empire

[O]ne of the names of a locust is, "Arbeh," not much unlike in sound to an Arab. To which may be added, that it is a tradition of the Arabians, that there fell locusts into the hands of Mahomet [Mohammad], on whose backs and wings were written these words;

"we are the army of the most high God; we are the ninety and nine eggs, and if the hundred should be made perfect, we should consume the whole world, and whatever is in it."

And it was a law established by Mahomet, ye shall not kill the locusts, for they are the army of the most high God; and the Mahometans fancy that the locusts were made of the same clay as Adam was: and besides the tradition before mentioned, they say, that as Mahomet sat at table a locust fell, with these words on its back and wings;

"I am God, neither is there any Lord of the locusts besides me, who feed them; and when I please I send them to be food to the people, and when I please I send them to be a scourge unto them;"

...five months is the time that locusts live, and are in their strength and power, even the five, hottest months in the year, from April to September.