The Achaemenid conquest of the Indus Valley refers to a process beginning in the 6th century BCE and ending in the 4th century BCE, whereby the Achaemenid Persian Empire established control over the northwestern regions of the Indian subcontinent, today predominantly comprising the territory of Pakistan. The first of the two main invasions was conducted around 535 BCE by Cyrus the Great, who annexed the areas to the west of the Indus River, consolidating the early eastern border of the Achaemenid Empire. With a brief pause after Cyrus' death, the campaign continued under Darius the Great, who began to re-conquer former provinces and further expand Persia's political boundaries. Around 518 BCE, Persian armies under Darius crossed the Himalayas into India to initiate a second period of conquest by annexing regions up to the Jhelum River in Punjab.
The first secure epigraphic evidence through the Behistun Inscription gives a date before or around 518 BCE. Persian penetration into the Indian subcontinent occurred in multiple stages, starting from northern parts of the Indus River and moving southward. As mentioned in several Achaemenid-era Persian inscriptions, the Indus Valley was formally incorporated into the Persian realm through provincial divisions: Gandāra, Hindush, and Sattagydia.
Persian rule over the Indus Valley decreased over successive rulers and formally ended with the Greek conquest of Persia, led by Alexander the Great. This brief period gave rise to independent Indian kings, such as Abisares, Porus, and Ambhi, as well as numerous , which would later confront the Macedonian army as it massed for Alexander's Indian campaign. The Achaemenid Empire set a precedence of governance through the use of satrapies, which was further implemented by Alexander's Macedonian Empire, the Indo-Scythians, and the Kushan Empire.
Background and invasion
For millennia, the northwestern part of India had maintained some level of trade relations with the Near East. Finally, the Achaemenid Empire underwent a considerable expansion, both east and west, during the reign of Cyrus the Great (c.600–530 BC), leading the dynasty to take a direct interest into the region of northwestern India.
Cyrus the Great
The conquest is often thought to have started circa 535 BCE, during the time of Cyrus the Great (600-530 BCE). Cyrus probably went as far as the banks of the Indus river and organized the conquered territories under the Satrapy of Gandara (Old Persian cuneiform: 𐎥𐎭𐎠𐎼, Gadāra, also transliterated as Gandāra since the nasal "n" before consonants was omitted in the Old Persian script, and simplified as Gandara) according to the Behistun Inscription. The Province was also referred to as Paruparaesanna (Greek: Parapamisadae) in the Babylonian and Elamite versions of the Behistun inscription. The geographical extent of this province was wider than the Indian Gandhara. Various accounts, such as those of Xenophon or Ctesias, who wrote Indica, also suggest that Cyrus conquered parts of India. Another Indian Province was conquered named Sattagydia (𐎰𐎫𐎦𐎢𐏁, Thataguš) in the Behistun inscription. It was probably contiguous to Gandhara, but its actual location is uncertain. Fleming locates it between Arachosia and the middle Indus. Fleming also mentions Maka, in the area of Gedrosia, as one of the Indian satrapies.
Darius I
A successor of Cyrus the Great, Darius I was back in 518 BCE. The date of 518 BCE is given by the Behistun inscription, and is also often the one given for the secure occupation of Gandhara in Punjab. Darius I later conquered an additional province that he calls "Hidūš" in his inscriptions (Old Persian cuneiform: 𐏃𐎡𐎯𐎢𐏁, H-i-du-u-š, also transliterated as Hindūš since the nasal "n" before consonants was omitted in the Old Persian script, and simplified as Hindush), corresponding to the Indus Valley. The Hamadan Gold and Silver Tablet inscription of Darius I also refers to his conquests in India.