Key point: Billions would perish if Beijing and New Delhi went nuclear.

A hypothetical war between India and China would be one of the largest and most destructive conflicts in Asia. A war between the two powers would rock the Indo-Pacific region, cause thousands of casualties on both sides and take a significant toll on the global economy. Geography and demographics would play a unique role, limiting the war’s scope and ultimately the conditions of victory.

India and China border one another in two locations, northern India/western China and eastern India/southern China, with territorial disputes in both areas. China attacked both theaters in October 1962, starting a monthlong war that resulted in minor Chinese gains on the ground.

Both countries’ “No First Use” policies regarding nuclear weapons make the outbreak of nuclear war very unlikely. Both countries have such large populations, each over 1.3 billion, that they are essentially unconquerable. Like all modern wars, a war between India and China would be fought over land, sea, and air; geography would limit the scope of the land conflict, while it would be the air conflict, fought with both aircraft and missiles, that would do the most damage to both countries. The trump card, however, may be India’s unique position to dominate a sea conflict, with dire consequences for the Chinese economy.

A war between the two countries would, unlike the 1962 war, involve major air action on both sides. Both countries maintain large tactical air forces capable of flying missions over the area. People’s Liberation Army Air Force units in the Lanzhou Military Region would fly against Punjab, Himchal Pradesh and Uttarakhand and from the expansive Chengdu Military region against India’s Arunachal Pradesh. The Lanzhou district is home to J-11 and J-11B fighters, two regiments of H-6 strategic bombers, and grab bag of J-7 and J-8 fighters. A lack of forward bases in Xinjiang means the Lanzhou Military Region could probably only support a limited air campaign against northern India. The Chengdu Military Region is home to advanced J-11A and J-10 fighters but there are relatively few military airfields in Tibet anywhere near India.

Still, China does not necessarily need tactical aircraft to do great damage to India. China could supplement its aerial firepower with ballistic missiles from the People’s Liberation Army Rocket Forces. The PLARF overseas both nuclear, conventional and dual-use ballistic missiles, and could conceivably move up to two thousand short- and medium-range DF-11, DF-15 and DF-21 ballistic missiles into positions adjacent to India. These missiles could be used to blitz Indian strategic targets on the ground, at the cost of making them unavailable for contingencies in the South and East China Seas.

Meanwhile, India’s air forces are in a better position to contest the skies than their Chinese counterparts. While the war would take place on China’s sparsely manned frontier, New Delhi is only 213 miles from the Tibetan frontier. India’s air fleet of 230 Su-30Mk1 Flankers, sixty-nine MiG-29s and even its Mirage 2000s are competitive with or even better than most of China’s aircraft in theater, at least until the J-20 fighter becomes operational. India likely has enough aircraft to deal with a two-front war, facing off with Pakistan’s Air Force at the same time. India is also fielding the Akash medium-range air defense missile system to protect air bases and other high-value targets.

While India could be reasonably confident of having an air force that deters war, at least in the near term, it has no way of stopping a Chinese ballistic-missile offensive. Chinese missile units, firing from Xinjiang and Tibet, could hit targets across the northern half of India with impunity. India has no ballistic-missile defenses and does not have the combined air- and space-based assets necessary to hunt down and destroy the missile launchers. India’s own ballistic missiles are dedicated to the nuclear mission and would be unavailable for conventional war.

The war on the ground between the Indian and Chinese armies might at first glance seem like the most decisive phase of the war, but it’s actually quite the opposite. Both the western and eastern theaters are in rugged locations with little transportation infrastructure, making it difficult to send a mechanized army through. Massed attacks could be easily stopped with artillery as attacking forces are funneled through well-known valleys and mountain passes. Despite the enormous size of both armies (1.2 million for the Indian Army and 2.2 for the Chinese Army) fighting on the ground would likely be a stalemate with little lost or gained.

The war at sea would be the decisive front in a conflict between the two countries. Sitting astride the Indian Ocean, India lies on China’s jugular vein. The Indian Navy, with its force of submarines, aircraft carrier INS Vikramaditya and surface ships could easily curtail the the flow of trade between China and Europe, the Middle East, and Africa. It would take the Chinese Navy weeks to assemble and sail a fleet capable of contesting the blockade. Even then, the blockade would be hard to break up, conducted over the thousands of square miles of the Indian Ocean.

Meanwhile, shipping to and from China would be forced to divert through the western Pacific Ocean, where such diversions would be vulnerable to Australian, Japanese, or American naval action. 87 percent of the country’s petroleum needs are imported from abroad, particularly the Middle East and Africa. China’s strategic petroleum reserves, once completed sometime in the 2020s, could stave off a nationwide fuel shortage for up to seventy-seven days—but after that Beijing would have to seek an end to the war however possible.

The second-order effects of the war at sea would be India’s greatest weapon. War jitters, the shock to the global economy, and punitive economic action by India’s allies—including Japan and the United States—could see demands for exports fall, with the potential to throw millions of Chinese laborers out of work. Domestic unrest fueled by economic troubles could become a major problem for the Chinese Communist Party and its hold on the nation. China has no similar lever over India, except in the form of a rain of ballistic missiles with high-explosive warheads on New Delhi and other major cities.

A war between India and China would be nasty, brutal and short, with far-reaching consequences for the global economy. The balance of power and geographic constraints means a war would almost certainly fail to prove decisive. Both sides have almost certainly concluded this, which is why there hasn’t been a war for more than fifty years. We can only hope it stays that way.

Kyle Mizokami is a defense and national-security writer based in San Francisco who has appeared in the Diplomat, Foreign Policy, War is Boring and the Daily Beast. In 2009 he cofounded the defense and security blog Japan Security Watch. You can follow him on Twitter: @KyleMizokami. (This article originally appeared in 2017.)

Image: Reuters