The Emirates of Hirat was located near to Kufah in Iraq. Nowadays, Hirat is in a place known as Najaf at the bank of Euphrates river at its west while at the southeast is the tomb of our imam Ali r.a. The climate there is of hill climate as there are hills closer to the area.
At the west of this state, there was no other states anymore. So, the Bedouins had no other areas to roam around anymore. They just settled there. In the beginning, they just sold their sheep and camels. Later on, they feel comfortable so they make the place as their living place. Majority of the people in Hirat are the mixture of original Arabs with others.
This Emirates as mentioned earlier was founded by 'Amr ben Ady around 240 CE. His kingdom was recognized by Persia as Persia looked at it as a buffer state for them. Their borders would be protected by this kingdom when other Arabian tribes attacking them and they could also serve as Persian frontier. According to the rules in the period, Hirat was a protectorate kingdom of Persia. Each crowned prince of the kingdom who would ascend the throne must bear the testimony that they will be loyal to the Persian emperor and protecting Persia if there are enemies attacking it.
As the favor, Persia will provide its assistance to Hirat without any tax and tribute to the emperor. All of the states in Persian empire posses their own autonomy power. There were governors or kings of their own who ruled the state and the emperor would be protecting the states. Differently to Roman empire, where it exercised centralized administration. If the king or the governor of a state wanted to set up a new rule and regulations for his state, he must ask for the permission of Roman emperor in Constantinople.
Other kingdoms in Arabian Peninsula were the Kindah and the Ghassan and they tried to spread their influence to further south. Some of Southern Arabian were the off-springs of Isma'el a.s through 'Adnan. Their elders and princes had no particular governance system, no systematic rules, no forts, no territorial marks and no large armies. While Roman empire was weak, Persian empire had authorized Hirat Emirates to develop their state according to their own way. Thus, Hirat became a wonderful trading center in the north and they became the portal for Persians to access Arabian Peninsula. Persian products were brought into Arabian Peninsula and sold there. It enhanced the economy of both Persian and Arabs territories.
Sedeliout said, the Hirat rulers were the off-springs of Qudha'a of 'Adnan the 41st generation of Isma'el a.s. They were the members of Tanukh clan. They entered Iraq through Bahrain and Tihama. They gained power in Hirat around 192 CE when they attacked Iraq. Later, they invaded al-Anbar and their leader at that time was Juzaima al-Abrash. He recognized Persia as their protector empire and thus was given the title of honor by Persian emperor. The Persian emperor at that time was Ardashir of Sassanid dynasty.
Then, he was replaced by 'Amr bin 'Ady who officially had formed Hirat kingdom as it was and he was known as the Lakhmide. This kingdom stays there until 605 CE. The Romans and Persians were rivaling to spread their influence around Euphrates river. At that time, Hirat was a small kingdom and it seeks for a protector empire to protect the kingdom. Since they were of close proximity to Persia, so Persia became their protector empire. In 272 CE, they managed to defeat areas around Euphrates and Tigris. Their influence thus reached Antioch. When their kingdom expanded, they find that it is difficult to maintain their tributary kingdoms.
So long that Persians and Romans confronted each other. If Roman wins the war, Hirat would be doomed as Roman perhaps would seek revenge on them. Few times that Romans tried to attack them for e.g in 289, in 353 and in 363 CE, they managed to break into Southern Arabia. The Romans succeeded in conquering al-Anbar and defeated al-Munzer I in 421. In 498 CE, Persian waged war with the Romans. Emperor Anstace was defeated and the whole Mesopotamia was free from Roman influence in 502 CE.
In 503 CE, Nu'man III with his associate, Persian empire chased the Romans out. The Taghalib and Bakr clan were also involved as they were following their prince, al-Harit bin Amir. Al-Harit bin Amir was a follower of Mazdak religion. Because he was of the same religion with Persian empire, his relationship with them was quite close. He chased al-Munzer III from his throne in 515 CE. The later Persian emperor does not support Mazdak religion anymore. So, al-Harit had lost his royal support. He was overthrown by al-Munzer III.
Al-Munzer III tried to protect Hirat and the Arab areas under Persian protection. They were involved in the battle with the Byzantine Romans until they gave up to expand their areas into Arabian Peninsula. Hirat was a developed kingdom during the reign of al-Munzer III and it continues to be so until the reign of Nu'man V who ruled at 583-605 CE. Nu'man was the last Hirat king from Lakhmide dynasty. After he passed away, Hirat was absorbed into Persian empire. Not as a protectorate anymore but as a Persian state until the rise of prophet Muhammad s.a.w.
Henry Masset in his thesis said that the origin of Southern Arabs were of Northern Arab caravans moved into Southern Arabian Peninsula. They later established few Emirates in various forms and systems. At the border of Syria, there were the Ghassanides who were recognized by the Byzantine Romans in Constantinople. They were protecting Romans' territories. Then, the Lakhmides who established Hirat Emirates while being used as Persian empire as their buffer state.
Both of these Arab nations were influenced by their empires in enmity because of the empires' wars. Hirat Emirats was a center of Christianity and once a learning center. The first Lakhmide king who passed away in 328 CE was actually a Nestorian Christian despite of his good relationship with Persians.
Sealed with prayers for mercy, peace and love, amin!