The below mentioned article provides notes on the Persian Occupation of India.
When the rulers of Magadha were extending their empire in India, the kings of Persia were also busy establishing their foot-hold on India. Cyrus, the founder of the Persian Empire conquered the areas up to Hindukush and Gandhara formed a part of his empire.
Darius I, another ruler of the Persian Empire sent his admiral Skylax to explore the mouths of Indus river. This was followed by an expedition to India in 517-516 B.C., which resulted in the annexation of the territory of Punjab to the Persian Empire. Persian governors and district officers were stationed in the province of Punjab.
The Persian conquest of India was of great significance. For the first time India came into contact with the western world. This contact proved of immense benefit to the people of Persia and India.
It not only lead to increased commercial and cultural intercourse between the two countries but also led to interchange of the social and political ideas between the two countries. Above all it provided an impetus to the unification of Northern India under the Sungas and the Mauryas.
The Persians introduced into India the Armaic form of writing which subsequently developed into Khroshthi script According to certain scholars the pillared hall of Asoka at Pataliputra, his edicts on pillars and rocks, his pillars with round-bell shaped abaci and lion capitals were influenced by Persian art and architecture.
Some of the prevailing social customs of India also testify to a close influence of the Greek influence. It is held that Chandragupta introduced a number of Persian ceremonials at his court. However, the Persian influence was confined only to the areas covered by Indus and its tributaries.