Cadusii

The Cadusii (, Kadoúsioi; lat.: Cadusii) were an ancient Iranian people living in north-western Iran.
Origin.
The original inhabitants of Gilan were the tribes of Cadusii (heirs of the ancient star-seekers), the area of which was the residence of the mythical kings of the Keyanids. George Rawlinson considers the Cadusii to be a tribe of Aryan origin. Titus Livius considered the Cadusii and Medes to be a people of the same origin. The Cadusii , according to Fuller and Humphrey Prideaux, were Israelites - their name Kedushim in Hebrew means "holy people." Cadusii and Caspians mentioned by Herodotus and located in the same territory, according to some authors, refer to barbarians of Scythian origin. William Smith and some other authors write about the scythian origin of the Cadusii.
Hypothesis of Germanic origin
According to "Georgy Telezhko", the traditions of the Chatti and the Cadusii are similar, according to the tales of Tacitus and Greek historians: both peoples have an election of leaders, a noticeable preponderance of infantry over cavalry, settle in the mountains. The Chatti of Asia Minor are also known - the ancient autochthons of Asia Minor. Presumably the Cadusii are former residents of Hattusa, which was the capital of the kingdom of the Hatti. Perhaps a comparison of the Cadusii and the Chatti of Asia Minor is not a necessary condition for the observed continuity of the Cadusii at the Germanic Chatti”.
Cadusii language.
The Cadusii language("Scythian Gelae"), according to some authors, was identical to the language of the Sakas Sakasene from the Behistun inscription. 
Yulian Bromley and some other linguistic historians consider the Cadusii an Iranian-speaking tribe. 
Johannes Albrecht Bernhard Dorn in his book ""On the campaigns of the ancient Russians in Tabaristan", guided by the opinion of "Richard Gosche", equates the Cadusii language with the Daylami language.
The names and leaders of the Cadusii.
E.Grantovsky argues that the famous names of the Cadusii were Iranian. Charles Rollin indicates that the cadusii had two leaders. 
George Rawlinson, along with Israel Smith Clare, in his book calls one of the leaders of the Cadusii as "Aphern" or "Onaphernes"". 
Plutarch cites the name of the leader of the cadusians as "Artathe"
On kinship with the Daylamites.
Ancient authors mistakenly attribute Cadusii to the Elamites,but later writers still point out that the Elamites were mistakenly associated with the Daylamites.
About the attitude to the scythian gelae.
Strabo ("Lib, XI. P.10") said that from the Hyrcanian Sea (Caspian) to the east on the right side to India there are mountains called Taurus by the Greeks. On the northern side of these mountains live Gelae and Cadusii,to the left live the Dahae, to the east the Massagetae and Sacae, and others, called by the common name Scythians.
Pliny (Lib, VI. Sar.XVIII) wrote that the Greeks called the Gelae as Cadusii, as well as on the northern side of the Taurus, next to the gelae and cadusii (dokusini), he supposing Aorsi, which the Greeks also called Cadusii. Probably, dokusini (Docusini from the word Dahae) are the same with Dacians, Aorsi and Gelae.
Theophanes of Mytilene, who took part in a military campaign among the Albanians, noted that the Gelae and Legae are Scythians and they are live between the Amazons and the Albanians.
Geography.
The Cadusii lived in Cadusia – a mountainous district of Media Atropatene on the south-west shores of the Caspian Sea, between the parallels of 39° and 37° North latitude. This district was probably bounded on the North by the river Cyrus (today Kura, in the former Soviet Republic of Azerbaijan, historically known as Arran and Caucasian Albania), and on the South by the river Mardus (today Sefid River), and corresponds with the modern Iranian provinces of Gilan and Ardabil.
They are described by Strabo as a warlike tribe of mountaineers, fighting chiefly on foot, and well skilled in the use of the short spear or javelin. It is possible that the name of the Gelae (Gilites) – a tribe who are constantly associated with the Cadusii, to the point of considering the former the national name for the Cadusii – has been preserved in the modern "Gilan".
No mention of the Cadusii has been found in Caucasian or Middle Eastern sources, and they are known only through Greek and Latin sources.
History.
Before the Persian Empire.
They appear to have constantly been at war with their neighbours. First subjected by the Assyrians, if we believe to Diodorus' doubtful sources, they were then brought in at least nominal subjection to the Medes, until they rebelled at the time of the king of the Medes Artaeus. In Ctesias' tale (reported by Diodorus) the war originated from an offence the king gave to an able powerful Persian, called Parsodes. After the offence Parsodes retired himself in the Cadusii's land with a small force and he attached himself with the most powerful of the local lords by offering his sister in marriage to him. At this point the country, who was subject to at least a nominal subjugation to the Medes, rebelled and chose as its war-leader Parsodes, giving him command of their army. Against these the Medes armed no less than eight hundred thousand men (these are the numbers given by Ctesias, which shouldn't be given much trust). Artaeus failed miserably in his attempt to reconquer the Cadusii and Parsodes was triumphantly elected king by the winners. Parsodes waged continuous raids in Media for all his long kingdom, and so did those who succeeded him, generating a state of perpetual enmity and warfare between Cadusii and Medes that continued until the fall of the Medes in 559 BC. But it must be remembered that all Greek records on the East before Cyrus must be treated with the utmost skepticism. This said, it may be that behind this legend there is a part of truth if we believe some scholars who identify Artaeus with Herodotus' Deioces, or better Duyakku, an important Mede chief in the age of Assyrian hegemony. Another point of interest in this story is that Ctesias here mentions for the first time the Cadusii. What seems more certain (in the report of Nicolaus of Damascus) is that near to the end of the Mede kingdom the Cadusii played an important role in bringing its downfall by allying themselves with the Medes' enemies, the Persians.
Cadusii and Persians.
It does not seem that the Persians had initially great difficulties in submitting the Cadusii; they were immediately loyal allies of Cyrus the Great (559–529 BC), firstly against the Medes and secondly against the Babylonians. And their submission seems to have been something more than nominal considering that Xenophon tells us that Cyrus assigned to a son called Tanaoxares (probably Smerdis) the satrapy of Cadusia. But by the times of Darius the Great Persian full control on the region must have suffered a partial setback, since we never hear their name in Herodotus or in Persian inscriptions in the lists of peoples and territories being part of the empire. In an unknown year they had been, it would seem, successfully submitted and probably added to the satrapy of Media or that of Hyrcania; this because it is told that in 406 BC Cyrus the Younger, a son of the High King Darius II (423–404 BC), had just led an expedition against the Cadusii in revolt. Cyrus' expedition was a success as three years later the Cadusii fought at Cunaxa under the banners of Artaxerxes II (404–358 BC) against Cyrus. But their obedience to Artaxerxes II didn't keep long; we see them rebelling in 385 and 358 BC. The first rebellion was defeated by a great army led by the same Artaxerxes. In the victory paid a key role the king's advisor Tiribazus, who smartly tricked the chief rebels in submitting themselves to the king. Another man who distinguished himself in the campaign was Datames, who would rise to become one of the most brilliant Persian generals. The conflict of 358 under Artaxerxes III (358–338 BC) was the last major clash between Cadusii and Persians; for the last years of the empire the Cadusii remained submissive. This war was important since it gave an occasion for the Persian general Codomannus, to distinguish himself in a sole combat against a Cadusian chief; an action that paved him the road to the throne as Darius III (336–330 BC).
Alexander the Great and aftermath.
In the Macedonian conquest of the east the Cadusii remained loyal to the Persians all the way up to Darius III's bitter end; we read of their cavalry fighting against Alexander at Gaugamela (331 BC) and of preparing to send reinforcements to the High King after the battle. But at the end they were subdued by Alexander's general Parmenion. In the subsequent Eastern wars they are mentioned as the allies of one or other party. After the division of Alexander's empire they became part of the Seleucid empire; in this context we read of them fighting for the Seleucids in the battle of Raphia against the Egyptians (217 BC), and their name is cited by Antiochus III's (223–187 BC) envoys at Aegium to the Achaeans as one of the many people under the sway of the Seleucids. But the crushing Romans victory at Magnesia started the disintegration of Seleucid power and the loss of all eastern territories. From this moment, little is known of Cadusian history; they seem to have been early submitted by the Parthians. As their allies Mark Anthony met them in 36 BC during his Parthian campaign; and two centuries later Caracalla in 216 repeated the campaign also entering in contact with the Cadusii. Excepting a forged letter by a Cadusian chief named Velonus to the Sasanian king Shapur I in 260, this is practically the last source that speaks of the Cadusii as an existing people; at this point they seem to vanish probably merging with other Caspian tribes. Modern day Talysh people generally identify themselves with the ancient Cadusians.