The Janapadas were the major kingdoms of Vedic India. By the 6th century B.C. there were approximately 22 different Janapadas. With the development of iron in parts of UP and Bihar, the Janapadas became more powerful and turned into Mahajanapadas. There were sixteen such Mahajanapadas during 600 B.C. to 325 B.C. in Indian Sub-continent.
Magadha Empire ruled from 684 B.C - 320 B.C in India. The Magadha Empire is mentioned in the two great epics Ramayana and Mahabharata. There were three dynasties who ruled Magadhan empire from 544 BC to 322 BC. The first one was Haryanaka dynasty (544 BC to 412 BC), second one was Shisunaga Dynasty (412 BC to 344 BC) and the third one was Nanda dynasty (344 BC-322 BC).
There were two major foreign invasions of Indian Sub-continent which happened in the form of Iranian invasion in 518 BC and Macedonian invasion in 326 BC. These two invasions promoted Indo Iranian Trade and commerce. Iranian writers introduced Kharoshthi script in India which was later on used in some Ashokan inscriptions. It was written from right to left like Arabic.
The Satavahana Empire existed around 230 BC onwards in India and extended from Dharanikota and Amaravati in Andhra Pradesh to Prathistan and Junnar in Maharashtra. The empire lasted 450 years approximately which is 220 AD. In fact, the Satavahana started off as the vassals of Mauryan Empire and after their decline emerged as the independent empire in south India.
In the sixth century BCE, there was a rise in the development of a few kingdoms that became prominent and earned the name Mahajanapada or great country. Aryans were the most influential tribes and were called as ‘janas’. This gave rise to the term janapada where jana means ‘people’ and pada means ‘foot. Janapada were the major kingdoms of Vedic India. A new kind of socio-political development was taking place in Mahajanapada. Mahajanapada were located in distinct geographical zones. There were sixteen such Mahajanapadas.
The foundation of the Mauryan Empire opens a new era in the history of India. For the first time, the political unity was achieved in India. Moreover, the history writing has also become clear from this period due to accuracy in chronology and sources. Besides plenty of indigenous and foreign literary sources, a number of epigraphical records are also available to write the history of this period. Contemporary literature and Archaeological findings are crucial sources of information.