The foundation of the Maurya empire in B.C. 324 or 321 by Chandragupta Maurya was a unique event in history, particularly in view of the fact it was founded shortly after Alexander’s victorious campaigns in North-West India during B.C. 327- 325.
The Greek invader after conquering North- West India had established a formidable foreign rule in the country and Alexander placed his newly conquered areas under the Satraps appointed by him.
The northern and eastern part of India, with capital at Pataliputra, was under the powerful and extremely rich, but unpopular and oppressive, rule of the Nandas. The last Nanda ruler was nicknamed as Dhana Nanda on account of the vast treasure accumulated by him by means of excessive taxation and exactions.
The Puranas refer to him as Mahapadma Nanda or Mahapadmapati while the Greek sources call him as Agrammes, which has been transliterated as Ugrasena Nanda by some modern historians. The Buddhist sources and Mudrarakshasa refer to a well known story mentioning the last Nanda king insulting Brahman Chanakya in his court, whereupon Chanakya vowed that he would avenge himself on Nanda by bringing about the destruction of his whole family and progeny.
To achieve his aim he educated and groomed Chandragupta to liberate the Northwest India from the foreign Greek rule and to overthrow the Nandas from Magadha. Chandragupta Maurya after achieving the above objectives in or about 321 B.C. moved towards unifying other parts of the country under his rule.