He doesn't mention the book's name. Also "Indian Maharajah's before the British came" is a ridiculously vague statement. In the period immediately preceding British rule, the Mughal Empire held sway over much of India. Maharajah is a Hindu term, you would be hard pressed to find a Maharajah with a large army outside of Rajasthan and parts of Maharashtra. Since he gives no clear time/space reference the statement has very little value.

As for warlikeness in general, it is true that war in some form or other was prevalent in India in pre-British times, the last great Mughal Emperor Aurangzeb spent a large part of his life fighting a campaign against the Marathas, and with the decline of the Empire, a number of wars were fought between the smaller regional powers. But what needs to be understood is that this was not an exceptional phenomenon, in context of Europe. India is as large as a major portion of Europe and harboured a number of political powers. While India saw a lot of conflict in the late 17th and 18th centuries, Europe itself fought the huge, catastrophic Thirty Years War in the first half of the 17th Century and the 14th, 15th and 16th centuries saw a number of conflicts across the length and breadth of Europe.

Interestingly the British in India were almost always mired in war before 1857. They fought the Carnatic wars with France as an extension of the Seven Years War. They fought in Bengal to secure a political power centre, then they fought against the powerful state of Mysore in South India, then against the Marathas, and finally the Sikhs in the Punjab. The Revolt of 1857 was the last time the British fought a large scale war in India, though there were foreign adventures like the Afghan and Burmese wars and the invasion of Nepal. Indian nationalists would later argue that the British army in India took up a disproportionately large part of the revenue. This source puts the army's share of the revenue at 33%/

So clearly the issue is a bit more complicated than what is implied in the video