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The Maurya Empire (322–185 BCE) was the first empire to unify India into one state, and was the largest on the Indian subcontinent. At its greatest extent, the Mauryan Empire stretched to the north up to the natural boundaries of the Himalayas and to the east into what is now Assam. To the west, it reached beyond modern Pakistan, to the Hindu Kush mountains in what is now Afghanistan. The empire was established by Chandragupta Maurya in Magadha (in modern Bihar) when he overthrew the Nanda Dynasty. Chandragupta's son Bindusara succeeded to the throne around 297 BC. By the time he died in c. 272 BC, a large part of the subcontinent was under Mauryan suzerainty. However, the region of Kalinga (around modern day Odisha) remained outside Mauryan control, perhaps interfering with their trade with the south.

What was the first empire to unify India?
Maurya Empire