Hi everyone,
I am currently invested in John Keay's China A History, in which he claims that in 649 Tang China sent a punitive Sino-Tibetan force across the Himalayas and into Bengal as repayment for the hostile reception Chinese Buddhist emissary Xuanzang received during the chaos of the collapse of the Pushyabhuti dynasty of India. To quote the text word for word:
It was thus a joint Sino-Tibetan force that in 649, probably by way of the Chumbi pass between Sikkim and Nepal, crossed the Great Himalaya and inflicted a heavy defeat on Harsha's successors ... The Sino-Tibetan incursion probably affected only a corner of Bengal and had no known repercussions. Though a Chinese assault on Indian territory had been shown to be feasible, it would not be repeated until the 1960s.
My question is why this was the case? Was the rationale for a more hands off approach to India [as opposed to South East Asia, Korea or the Xiongnu/Qaganates] purely economic or geographic? If the Tang Emperor knew his troops were capable of force projection in this region why did neither he nor any successors of any dynasty even attempt such action again?
While not an expert on Indian-Chinese history I can lend a perspective on why Chinese groups didn't attempt to move into India. The main reason was the fact that China had nothing to gain. The geography separating China and India makes moving between the two with a large group troublesome and the economic benefit of annexing a part of India would have been minimal. There was nothing in India that China didn't have access to or need.