China is easily India's biggest foreign policy concern today, and military too. The chief of Army staff spoke of India's preparedness to take China on in case of a conflict and a former ambassador to China is now foreign secretary. But an India-China expert, professor Tansen Sen of the New York University in Shanghai, is advocating it's time to engage with China differently; with caution over issues like Tibet, it's rising nationalism and growing influence in India's backyard. Professor Sen was in Kolkata to launch his latest book, India, China and the World: a connected history.