It was a nasty fight the first time. Myanmar, China, and Pakistan are all buddy-buddy, so perhaps not a cake walk this time either. Consider Spain's role in NATO. Those Russians were going to have to push a long way to get to Spain, but their border wasn't the logical place for the Spanish to start fighting the Russians.
Sorry. I don’t think that makes much sense.
India is 1.2B, Pakistan 180M people. It’s a little as if Canada was supposed to be worried about needing to defend itself against an invasion from Mexico.
Which leaves out of the equation that both Pakistan and India have nukes, now. Which if past history holds, as we can hope, means they won’t ever go back to fullbore war with each other.