Nadr Qoli Beg had an obscure beginning in the Turkish Afshar tribe, which was loyal to the Safavid shahs of Iran. After serving under a local chieftain, Nadr formed and led a band of robbers, showing marked powers of leadership. In 1726, as head of this group of bandits, he led 5,000 followers in support of the Safavid shah Tahmasp II, who was seeking to regain the throne his father had lost four years earlier to the Ghilzay Afghan usurper Mahmud. Nadr reformed Iran's military forces and utterly defeated the Ghilzay Afghans in a series of brilliant victories, after which he restored Tahmasp to the Iranian throne.

Nadr then attacked and routed the Ottoman Turks, who had occupied adjacent areas of Azerbaijan and Iraq. Meanwhile, Tahmasp had rashly attacked the Turks while Nadr was absent quelling a revolt in Khorasan, but the shah was heavily defeated and was forced to conclude peace with the Turks on ignominious terms. Enraged at this, Nadr hurried back, deposed Tahmasp, placed the latter's infant son on the throne, and declared himself regent. After sustaining a defeat at the hands of the Turks in Iraq, Nadr revenged himself by driving them completely out of Iran. Then, by threatening Russia with war, he forced that nation to relinquish its Caspian provinces to Iran. In 1736 Nadr deposed the youthful 'Abbas III (as Tahmasp II's son was styled) and ascended the Iranian throne himself, taking the title of Nadir Shah.

With the navy he proceeded to build, Nadir Shah was able not only to take Bahrain from the Arabs but also to invade and conquer Oman. In February 1739, after capturing several cities of the Mughal Empire of northern India, he moved against the main Mughal armies at Karnal, India. He won the battle and entered Delhi, returning to Iran with vast amounts of loot, including the fabulous Peacock Throne and the Koh-i-noor diamond. He then attacked the Uzbeks around the cities of Bukhara and Khiva; his empire had reached its furthest expansion and rivaled the territorial extent of the ancient Iranian empires.

In 1741, after an assassination attempt on him had failed, Nadir Shah suspected his eldest son of complicity and had him blinded. He also attempted to make the largely Shi'ite populace of Iran adopt the Sunni form of Islam. In 1743 Nadir Shah again attacked the Ottoman Turks, but revolts in Iran forced him to conclude a truce. He renewed hostilities with the Turks as soon as possible, winning a great victory over them near Yerevan. Peace was concluded in 1746.

Although brilliantly successful as a soldier and general, Nadir Shah had little talent for statesmanship or administration, and Iran became utterly exhausted during the later years of his reign. Tens of thousands of people perished in his ceaseless military campaigns, and the exactions of his tax gatherers ruined the country's economy. Nadir Shah had always been harsh and ruthless, but these traits became more pronounced as he grew older. His suspiciousness and capricious cruelty continued to grow, and wherever he went he had people tortured and executed. The consequence was that revolt after revolt against him occurred. In the end he was assassinated by his own troops while attempting to crush an uprising in Khorasan. Nadir Shah's only interests were war and conquest. Once, when informed that there was no warfare in paradise, he remarked: "How then can there be any delights there?"