In approximately 600 BCE, kings emerged out of the realms of tradition to set up and rule over several kingdoms stretching from the highlands of the north-west
frontier to the lowlands of the Ganges, and southwards across the Vindhya mountains till the Godavari river on the Deccan plateau. There were powerful and not-so-powerful kings, aggrandizing rulers who were aspirants to the appellation ‘chief king of all kings’, and powerful confederate clans. Over a relatively short period of time—roughly coinciding with the domination of Athens in the classical period—a large part of this profusion of political entities was absorbed into a single imperial realm. Centred in Magadha, which was based in the middle Gangetic plains of Bihar, a succession of kings ruled over this empire straddling large parts of India. The first of these imperial houses was that of the Nandas. They were followed by the Mauryas. From the fourth century BCE till the advent of Ashoka (c. 269/268 BCE), there were said to have been eleven such imperial monarchs, nine in the Nanda dynasty followed by the two Maurya kings who preceded Ashoka: Chandragupta, founder of the dynasty (Ashoka’s grandfather, who overthrew the Nandas), followed by Bindusara, Ashoka’s father. But though the king succeeded king and one century followed another, the only evidence of those times are versions of them—some accurate, others fanciful, and practically never contemporary—that have survived. These remaining records of those times are the Puranas, certain Buddhist and Jaina texts, and histories of a sort by people who are referred to as ‘classical authors’—mainly literate companions in Alexander’s entourage—as also the famous Megasthenes who visited the court of Chandragupta. These sources provide us with nearly all the information that we now have of India’s rulers and states in that antique time. The rulers themselves failed to speak to their subjects, and therefore to us. Many of their names, and of their principalities, are known: Janaka of Videha, Pasenadi of Kosala, the Magadha monarch Bimbisara, and Pradyota of Avanti are some. But how such kings defined their domains and powers, how they appeared to their subjects, what they and their queens donated, and what kind of worship prevailed in their courts—these remain hidden because no royal epigraphs or labelled sculptures, no coins carrying royal portraiture or the names of kings and queens, not even palaces or communications emanating from such places and people, have endured. It was only with the coming up of first inscriptions and edicts that emerged across the vast span of Indian subcontinent which were united for the first time under first Indian empire.
One of the greatest emperors of India - Chandragupta Maurya, uprooted the unethical rule of Dhana Nanda from royal stone and created the vast empire spanning almost all of the Greater India (Akhand Bharat). India's boundaries reached till Iran during Chandragupta's reign. Chandragupta Studied at Takshashila University-the most renowned University at that time. His teacher, Arya Chanakya guided Chandragupta throughout his life. Chandragupta Maurya defeated Seleucus I Nicator-the successor of Alexander, who was unable to invade India due to strong resistance from natives. [ref]
Bindusara was the son of the dynasty's founder Chandragupta and the father of emperor Ashoka. Bindusara consolidated the empire created by his father. The 16th century Tibetan writer Taranatha describes his administration with extensive territorial conquests across India. he states that Chanakya, Bindusara's teacher, destroyed the nobles and kings of 16 towns and made him master of all the territory between the western and the eastern seas of India (From Rajasthan to Bengal). [ref]
Bindusara was succeeded by his son Asoka who is one of the greatest figures in history. He was considered as the greatest of kings and that not because of the physical extent of his empire, extensive as it was, but because of his character as a man, the ideals for which he stood, and the principles by which he governed. As a king, he ruled over the greatest empire known in Indian history. The vast territory extending from Persia to Southern India was bequeathed to him by his predecessors. He himself made an addition to it by his conquest of the Kalinga.
A unique feature of his history is that he has himself left a record of it in a permanent form in inscriptions engraved on natural rocks as well as monolithic pillars constructed by him which stand to this day as remarkable monuments of Indian architecture and engineering skill. These inscriptions, along with the traditions recorded in literary texts in both Pali and Sanskrit, help to give a concrete and comprehensive picture of his life and work. [ref]