Persian Achaemenid Empire in c.520 BCE, during the reign of Darius the Great brought easterh Afghanistan and Pakistan under his rule and kept so for two centuries. In 326 BCE , Alexander the Great conquered Asia Minor and the Achaemenid Empire, reaching north-west frontier of the India subcontinent.There he defeated King Porus and conquered much of the Punjab.But his march towards east put him in confrontation with the Nanda Empire of Magadhaand the Gangaridai Empire of Bengal.His army exhausted and frightened by he prospect of facing larger Indian armies at the GangesRiver. Alexander decided to return.This was the first invasion from outside India as the Aryans were nomads and settled in India. 
