India and China have been nervously eyeing one another for decades Although neither of them has a rational reason to go to war with the other, strategists and political leaders in New Delhi and Beijing are making plans, building military roads and airbases, and thinking hard about what would happen if fighting were to break out somewhere along their disputed border. China has the world's second largest economy, India is ranked fourth. While India's economy may take a while to reach the size of China's its population may overtake China's within a decade or two. In spite of the understandable refusal by both governments to make it official, the rivalry between them is already shaping the geopolitics of the 21st century. The geographic context of their confrontation is unique. In October 1962, China and India fought a month-long war in the Himalayas over the disputed border there. The war ended with a Chinese military victory. Since then, that border has been quiet, but China's support for Pakistan, as well as its global ambitions, make both countries increasingly uncomfortable neighbors for India. Never before have two modern military powers -- China and India -- confronted one another across a mountain range like the Himalayas. The wars fought by Europeans across the alps and Pyrenees would appear as minor skirmishes compared to it. Control of the high ground has always been helpful in war, but now -- when controlling the high ground means better radar coverage, better intelligence gathering capability and better communications -- it is of supreme importance. A conventional war fought between these two rivals at very high altitude would superficially resemble the fighting between India and Pakistan during the 1999 Kargil conflict, when Pakistani infiltrators took control of some mountaintops on terrain claimed by India. Although they were eventually expelled by Indian forces in a month-long campaign fought in some of the most difficult conditions in the history of war, it is likely that a new confrontation here would quickly escalate into something far more intense. The extreme difficulty of resupplying ground forces fighting among the highest mountains in the would, for example, would rapidly make air superiority even more decisive than usual. Namely, for airpower and for modern precision weaponry to be fully effective, it must be supported by spacepower. Satellite navigation systems, such as America's GPSs, are essential, as are satellite communications, space-based reconnaissance and early warning systems. In the mountains, space systems are even more important than in level terrain because of the extreme difficulties of operating multiple fixed and mobile transmitters at high altitude. The limits of normal tactical radios at high altitude have become obvious to American forces operating in Afghanistan; in the Himalayas, the problems would be even worse due to the fact that the peaks are higher and the valleys deeper, making it is all too easy for a ground unit, or even an aircraft, to move into a communications dead zone. In Afghanistan the US has, to some extent gotten around this problem by using relay stations based on the ground, on aircraft and on drones, but even these relatively simple solutions have shown their limits. Relay stations cannot be everywhere; they are not responsive to quick changes in plans, and their placement can sometimes show the enemy where the US plans to send its troops. Although space systems may be essential to overcome these problems, they also have limits. Signals from ground based radio frequency communications systems or from navigation satellites can be blocked by mountains. Despite this problem, satellites are far more reliable as a means of communications than any available alternative, such as ground- or air-based relay transmitters. Another mode of warfare, dogfighting in high mountains, is a highly specialized art that is little understood outside a few places where it is essential to national survival. The Swiss Air Force has spent more than 70 years perfecting its ability to fight in the Alps. The main lesson it has learned is that training and maneuverability count for more than electronics or advanced weapons. A pilot who has flown into the same valley, or around the same mountain crest, hundreds of times will probably beat a pilot flying in the same environment for the first time, even if that pilot has been able to practice in a simulator. In the Himalayas, India would have the advantage when flying on its side of the border, and China would have the advantage on its side. Although both nations would naturally seek to train their pilots to fly on the other side of the line, it is hard to see how either side could develop a sustained advantage with an air force that used conventional information systems. If one side could gain an advantage using space-based assets, however, it would gain air superiority and thus win the air campaign, if not the war. If one side, for example, could gather data from space systems to give its pilots a precise awareness of where the enemy aircraft were, while denying such information to the adversary, it could win air superiority. The US has long been able to use satellites to put information into the cockpits of its military aircraft -- a capability that is proliferating both to America's allies and to its prospective foes. China and India are building and enhancing their military and quasi-military space assets. India recently launched another Earth observation satellite, adding to its existing constellation of surveillance spacecraft. India has also been working on a set of so-called GPS augmentation satellites, which would give India the capacity to adapt and tailor the GPS signal to its own specialized requirements. In spite of the failure of India's heavy launch rocket to put its latest communications satellite into orbit, it maintains a comprehensive array of these satellites. China has been pushing ahead with a comprehensive program aimed at building up its array of space assets. The Chinese are building their own global satellite navigation system called Beidou [Compass], which will be totally separate from America's GPS system. Members of the Chinese People's Liberation Army (PLA) have also been working hard to build improved communications and intelligence gathering satellites. The January 2007 test of an anti-satellite weapon signified that they take the possibility of space warfare deadly seriously. The Indians have not yet conducted a recognizable test of a anti-satellite weapons, but there are reports that indicate they may soon do so. The Indian military is hard at work developing indigenous missile defense technology, which they know can be adapted for use against satellites. If a conflict did erupt, both sides might believe that it would be to their advantage if they destroyed the other side's space systems. Even if the advantage of being the first to attack, using anti-satellite weapons, were short lived, it might last long enough to have a decisive military effect, especially if both sides came under diplomatic pressure to agree to a cease fire "in place." If the fighting spread to the high seas, or to the Pakistani frontier, or to both, the side with the best array of surviving space assets would have a considerable advantage. If there were fighting in the Indian Ocean, China would be more dependent on its space assets than India, which, thanks to geography, would find it easier to use UAVs and reconnaissance aircraft. The fact, however, that rivalries now extends into the Earth's orbit, simply shows just how important space power has become to any 21st century conflict.