Suren-Pahlavs & Deylamites
In the 6th century BCE, the inhabitants of Guilan (the Gil Gilanshah and Daylam) allied with Cyrus the Great and overthrew the Medes. Cyrus II conquered Media, Lydia and Babylon. Gilan was loosely allied with the Parthian and Sassanid empires. Following the rise to power of the Parthians, these seven clans shared the administration of the Parthian Empire, each governing a region of the empire. One of the more prominent clans was the Suren clan, to which Eran Spahbod Surena belonged.
Suren-Pahlavs were the member of Parni branch of the Aryan or better known as the Indo-Iranian Stock, a member tribe of the Dahae confederation, (Dahae-Parno-Parthian) tribes. The Suren-Pahlavs alongside the other members of the Parni, with Arsaces at their head, took the province of Parthovia (Parthia) after having beaten Andragoras and soon, neighbouring Hyrcania was annexed and the Caspian reached.
Deylamite mercenaries served in Persian armies and where generally considered the best infantry in the middle east up to the time of Mongol invasion.
While we know very little about the local customs of Gils and Deylamites, we know that some of their tribes originally revered the river Sepid Rud based on the evidence presented by the Greek geographer Strabo. These soldiers probably used Sagaris-type battle axes used by Scythian tribes by the Persians, Mossynoeci, and the Amazons. One such axe, known to the Classical Greeks was the labrys; a neolithic find of Old Europe which continued in Minoan, Thracian, Greek and Byzantine art and African myth, Shango. It was named from Lydian for Greek, double-edged axe. All Deylamite infantrymen carried a round, very large, and strikingly painted shield. In the Near East and other parts of the region, axes of this sort are often wielded by male divinities and appear to be symbols of the thunderbolt, but in Crete, unlike the Near East, this axe is never held by a male divinity, only by females.
Deylamite commander Vahriz (or Vahraz) was instrumental in the conquest of Yemen during the reign of Khosrau I (Anushirvan). Deylamite infantry men were legendry javeliners and had a fearsome reputation in using their battle-axes. They were not Zoroastrian prior to Sassanid overlordship, as evidenced by their custom of burying their dead and making human sacrifice.
Zoroastrianism gained ground during the Sassanid era. By the time of the Islamic invasion, Gils and Deylamites were Zoroastrian. Muslim chronicles of Varangian (Rus, pre-Russian Norsemen) invasion of the litoral Caspian region in the 9th century record Deylamites as non-Muslim. These chronicles also show that the Deylamite were the only warriors in the Caspian region who could fight the fearsome Varangian vikings as equals. Deylamite infantrymen had a role very similar to the Swiss Reisläufer of the Late Middle Ages in Europe. Deylamite mercenaries served as far as Egypt, Islamic Spain, and Khazar kingdom. Buyids established the most successful of the Deylamite dynasties of Iran. During the 900s, Buwayhid dynasties took power in Fars (southwestern Iran, 934-1062); Rayy (977-1029); Jibal (932-1028); Kerman (936-1048). From 945-1055, a Buwayhid dynasty ruled Baghdad and most of Iraq. During the mid 1000s the Buwayhid dynasties all fell to the Seljuks or their allies.