The Cambridge History of India, Vol. I: Ancient India v1.c31.27

v1.c31.27

It has been supposed that the introduction into India of the Persian and Parthian title, 'Great King of Kings,' was the result of an actual conquest of N.W. India by Mithradates I; and a statement of the historian Orosius that this monarch conquered all the peoples between the Hydaspes and the Indus has been interpreted to mean that he extended the power of Parthia beyond the Indus as far as the Indian Hydaspes (the Jhelum)¹. But to an author who is writing from the standpoint of Parthia, the expression 'between the Hydaspes and the Indus' must surely connote an extension from west to east—from a Persian river to the great Indus which has so often in history been the boundary between Irān and India. Hydaspes is a Persian name, and the river mentioned in this passage is no doubt the Medus Hydaspes of Virgil (*Georgics*, Ⅳ, 211)². The theory of a conquest of N.W. India by Mithradates I would therefore seem to be founded on a misunderstanding of the historian's statement. The invasion of India must be ascribed not to the Parthian emperors, but to their former feudatories in eastern Irān; not to the reign of Mithradates I, but to a period after the reign of Mithradates II, when the power of Parthia had declined and kingdoms once subordinate had become independent. The association to which the coins bear witness is not one between Parthia and eastern Irān, but between Irān and N.W. India. In fact, all through the period of Çaka and Pahlava rule the countries to the west and east of the Indus were governed by members of the same royal house. There were normally three contemporary rulers of royal rank—a King of Kings associated with some junior member of his family in Irān, and a King of Kings in India; and the subordinate ruler in Irān usually became in due course King of Kings in India.