The reason why it is so difficult to find a detailed account of the Mauryan usurpation of the Nanda empire is because no such account exists. The only near-contemporary historical sources which refer to Chandragupta Maurya's rise to power are Greeks sources like Plutarch and Diodorus Siculus (in which Chandragupta is referred to as "Sandrocottus" or "Androcottus"), but these Greek sources only describe the relevant events in very general terms and do not contain any detailed description of the strategy employed by Chandragupta Maurya. On the Indian end, the only sources which refer to this event in Indian history are much later, Gupta-era sources like the Mudrarakshasa by Vishakhadatta, a play on the topic of Chandragupta Maurya and his legendary minister/adviser Chanakya.

Obviously, the historical value of such a "source" is rather limited, but we might still be able to glean some insight from it. According to the Mudrarakshasa, Chandragupta Maurya had established an alliance with the "kings of Kashmir and Sindh" and formed a diverse army that included men from many different ethnic groups, including the Kambojas, Bahlikas, Yavanas, Sakas, and Parasikas. What is interesting about this description is that it clearly situates Chandragupta's initial base of power in the northwest of the subcontinent, where Kashmir and Sindh are located and where the various groups mentioned could be found. This seems to be in harmony with the minimalist description of Chandragupta found in Greek sources, which suggests that Chandragupta had led an army eastward into the Gangetic plains sometime around or after Alexander's invasion of India. We can only speculate on what exactly transpired between the Nandas and the Mauryas afterwards, but it seems likely that many of the leading officials/generals of the Nanda empire defected to the side of Chandragupta Maurya, which greatly contributed to the rapidity of the Mauryan usurpation. According to the Greek sources, the Nanda emperor was widely hated because of his "wickedness" and his "low birth," and this seems to be corroborated by the Indian Puranas (admittedly very late sources, once again) which describe the Nanda dynasty as low-born due to their founding member Mahapadma Nanda being the offspring of a servant woman.

The only facts that are established about Chandragupta's life and career after his usurpation of the Nanda throne are that he ruled Gujarat (which is established due to the Girnar inscription of Rudradaman), that he (re)conquered the northwestern areas of India sometime after 316 BCE from the subordinates/successors of the Greek governor-generals Eudamus and Peithon, and that he fought a war against Selecus Nicator between 305 and 303 BCE that eventually resulted in a marital alliance between the Seleucids and the Mauryas and the Mauryan acquisition of several provinces in modern-day Pakistan and Afghanistan.