Not so long ago, China and India were both colonized and pillaged by western imperialism. They have both been neighbors since ancient times and had (friendly) influences upon each other. I believe not once did one try to invade another in any significant way. Except, perhaps the Mongols, which by definition weren't 'Chinese' per se. It is wise to have friendly relations with those that live next to you. Otherwise, it is an unnecessary source of trouble. It is interesting to see, even after the hard work of expelling the imperialists out of their respective countries, they are still falling prey to the tactic of "divide and rule". Together, they can both become considerable powers. Against each other, there is a distinct possibility they will both ruin each other, if not constrain themselves to the benefit of someone else. The only winner out of the latter scenario will be the ones who actually invaded and pillaged both countries, not so long ago.