Koh-i-Noor leaves India for Persia, for the second time (1739-1747)

But unfortunately, during the rule of Muhammad Shah, the mighty conqueror Nadir Shah from neighboring Iran, invaded Delhi and Agra in 1739, and sacked the two cities and plundered their wealth. Nadir carried away Shah Jahaan's Peacock Throne, and all the crown jewels of the Mogul Emperors, which included the Koh-i-Noor, the Darya-i-Noor, Nur-ul-Ain etc. The total value of the loot carried away by Nadir Shah was estimated at 70 Crores (700 million rupees), and it is said that Nadir was able to exempt the Iranian people from taxes for the next three years. It was allegedly Nadir Shah who exclaimed Koh-i-Noor ! when he finally managed to obtain the famous stone, and this is how the stone gained it's name. There is no reference to this name before the year 1739. There is a legend attributed to one of Nadir Shah's consorts, which gives the valuation of the Koh-i-Noor, even though it is an unduly exaggerated estimate. According to this legend the consort is supposed to have said, "If a strong man should take five stones, and throw one north, one south, one east, and one west, and the last straight up into the air, and the space between filled with gold and gems, that would equal the value of the Koh-i-Noor."

Nadir Shah whose original name was Nadir Quli Beg, started life as a brigand chief, who formed and led a band of armed robbers. In 1726, he led a group of 5,000 followers in support of Shah Tahmasp II , who was trying to regain the throne, which his father had lost 4 years earlier to the Afghan ruler Mahmud. Nadir reorganized Iran's military forces, and utterly defeated the Afghans in a series of battles, and restored Thamasp II to the Iranian throne.

He then diverted his attention towards the Ottoman Turks, who had occupied neighboring Azerbaijan and Iraq. He attacked and routed them from these two countries. He later deposed Tahmasp II for signing a peace treaty with the Turks on ignominious terms, having attacked the Turks in his absence, when he was quelling a revolt in Khorasan. He placed Tahmasp's infant son on the throne and declared himself regent. Subsequently he succeeded in driving the Turks completely out of Iran, and also annexed the Russian Caspian Provinces. In 1736, Nadir deposed the young Abbas III (Tahmasp IIs son), and installed himself as the Shah, taking the title Nadir Shah.

Later he built a formidable Navy, that attacked and captured Bahrain and Oman. He then turned towards the east, and in 1739 attacked and captured several cities of the Mogul Empire, including Delhi and Agra. He returned to Iran with a vast amount of loot. later he attacked the Uzbeks near the cities of Bukhara and Khiva, and again attacked and defeated the Turks near Yerevan in Armenia.

As a conqueror, Nadir Shah succeeded in creating an Iranian Empire that stretched from the Indus River to the Caucasus mountains. Nadir was successful as a soldier and general, but he failed miserably as a statesman and administrator. He was harsh and ruthless towards his subjects. He was suspicious of everyone around him, and had people tortured and executed, wherever he went. Tens of thousands of people perished in his never ending military adventures. As a result he became very unpopular among his people, and had to face many revolts against him. Eventually, Nadir Shah was assassinated by his own troops in 1747, while attempting to crush a revolt in Khorasan.