Q1.
How do we know this?
Answer
Mainly from two kinds of sources, and the chapter names both:
- Archaeological excavations — digging has confirmed that those ancient urban centres really existed. Fig. 4.1 shows the ruins of a major structure at Rājagṛiha (modern Rajgir, Bihar), capital of Magadha; Fig. 4.4 shows a complex at Kauśhāmbī, capital of Vatsa; Fig. 4.7 shows a gateway and water-filled moat at Śhiśhupalgarh.
- Ancient literature describing them — late Vedic, Buddhist and Jain literatures are full of references to these new urban centres.
Why two sources are better than one: an excavation gives you real walls, ramparts, moats, coins and pottery, but it cannot tell you what a place was called or who ruled it. A text gives you names, kings and stories, but it may exaggerate. When the spade and the text agree — for example when a fortified site is dug up exactly where the texts place a mahājanapada's capital — historians can be confident.
Tip: the chapter itself then answers a second in-text question, ‘how did this phase emerge?’ — through clans forming janapadas, janapadas merging into mahājanapadas, iron tools making bigger harvests possible, and trade networks tying the settlements together.