If a war does happen, I believe India will win due to the fact that they have a larger economy, population, and more advanced air defense/Air Force. This is kinda tricky for India. Pakistan has pretty solid relations with China, who would provide arms to Pakistan. The US is tricky. While historically the US has been an ally of Pakistan, relations have really soured since the War on Terror began, and the US has started to improve relations with India more. Honestly I could see the US supplying either side or even both. Russia would align itself with India, as well as Japan. The EU would also probably focus on India, though it has trade agreements with Pakistan too. India would eventually win but it would take maybe several years more due to the supplies from other nations. Kashmir is a radioactive wasteland and Islamabad and New Delhi are burning. India might end up the victor due to a larger population, but it would be a hollow victory with millions dead at the end of the first week.