From reddit

"There's a good bit about this in the World War Z book. India and Pakistan have been on the brink of nuclear war for so long that there's tons and tons of tools and deterrents in place to prevent war. There's a nuclear hotline between states, all kinds of spies, well known procedures, etc that exist to prevent accidental or hasty all-out war. That's why in the book there's a nuclear exchange between Iran and Pakistan instead of Pakistan and India, because that diplomatic infrastructure doesn't exist between those two countries."

https://www.reddit.com/r/nottheonion/comments/tbqmq8/india_s...