Lord Wellington depicted the allied triumph at Waterloo as "the nearest-run thing you ever saw in your life." Wellington's verdict would describe the likely outcome should Chinese and Japanese forces meet in battle over the Senkaku/Diaoyu Islands, or elsewhere off the Northeast Asian seaboard. Such a fight appeared farfetched before 2010, when Japan's Coast Guard apprehended Chinese fishermen who rammed one of its vessels off the disputed islands, but it appears more likely now. After Japan detained and deported Chinese activists who landed on the disputed islands in mid-August, a hawkish Chinese major general, Luo Yuan, called on China to dispatch 100 boats to defend the Diaoyus. In an op-ed published Aug. 20, the nationalistic Chinese broadsheet Global Times warned, "Japan will pay a price for its actions ... and the result will be far worse than they anticipated."

　　This is more than mere posturing. In July, China's East Sea Fleet conducted an exercise simulating an amphibious assault on the islands. China's leaders are clearly thinking about the unthinkable. And with protesters taking to the streets to smash Japanese cars and attack sushi restaurants, their people may be behind them. So who would win the unlikely prospect of a clash of titans in the Pacific: China or Japan?

　　Despite Japan's latter-day image as a military pushover, a naval war would not be a rout for China. While the Japanese postwar "peace" constitution "forever renounces war as a sovereign right of the nation and the threat or use of force as means of settling international disputes," the Japan Maritime Self-Defense Force (JMSDF) has accumulated several pockets of material excellence, such as undersea warfare, since World War II. And Japanese mariners are renowned for their professionalism. If commanders manage their human, material, and geographic advantages artfully, Tokyo could make a maritime war with China a close-run thing -- and perhaps even prevail.

　　Past naval wars between the two rivals set the stage for today's island controversy. During the Sino-Japanese War of 1894-1895, a fleet engagement turned Asia's Sinocentric order upside down in an afternoon. The Imperial Japanese Navy, hurriedly cobbled together from imported hulls and components following Japan's Meiji Restoration, smashed China's Beiyang Fleet, a force widely considered superior in material terms. The September 1894 Battle of the Yalu River was won by the navy with superior seamanship, gunnery, and morale. While Japan is no longer a rising power, the JMSDF has preserved a culture of human excellence.

　　If a rerun of the Battle of the Yalu takes place, how would Japan's navy match up against China's? This is admittedly an improbable scenario. A straightforward China-on-Japan war is doubtful unless Beijing manages to isolate Tokyo diplomatically -- as wise practitioners of limited war attempt to do -- or Tokyo isolates itself through foolish diplomacy. Barring that, a conflict would probably ensnare the United States as an active combatant on the Japanese side. War is a political act -- "statesmanship directing arms," as naval historian Alfred Thayer Mahan puts it -- but let's discount politics for now and look at the prospects of war in strictly military terms, as a contest between Chinese and Japanese sea power.

　　In raw numerical terms, there is no contest. Japan's navy boasts 48 "major surface combatants," ships designed to attack enemy main fleets while taking a pounding themselves. For the JMSDF these include "helicopter destroyers," or light aircraft carriers; guided-missile destroyers equipped with the state-of-the-art Aegis combat system, a combination radar, computer, and fire-control system found in frontline U.S. Navy warships; and an assortment of lesser destroyers, frigates, and corvettes. A squadron of 16 diesel-electric submarines augments the surface fleet. Juxtapose this against the PLA Navy's 73 major surface combatants, 84 missile-firing patrol craft, and 63 submarines, and the bidding appears grim for Japan. China's navy is far superior in sheer weight of steel.

　　But raw numbers can be misleading, for three main reasons. First, as strategist Edward Luttwak has observed, weapons are like "black boxes" until actually used in combat: no one knows for sure whether they will perform as advertised. Battle, not technical specifications, is the true arbiter of military technology's value. Accurately forecasting how ships, planes, and missiles will perform amid the stresses and chaos of combat thus verges on impossible. This is especially true, adds Luttwak, when conflict pits an open society against a closed one. Open societies have a habit of debating their military failings in public, whereas closed societies tend to keep their deficiencies out of view. Luttwak was referring to the U.S.-Soviet naval competition, but it applies to Sino-Japanese competition as well. The Soviet Navy appeared imposing on paper. But Soviet warships on the high seas during the Cold War showed unmistakable symptoms of decay, from slipshod shiphandling to rusty hulls. The PLA Navy could be hiding something as well. The quality of the JMSDF's platforms, and its human capabilities, could partially or wholly offset the PLA's advantage of numbers.

　　Second, there's the human variable in warfare. In his classic account, The Naval War of 1812, Theodore Roosevelt explained the U.S. Navy's success in single-ship duels against Britain's Royal Navy as a product of quality ship design and construction and superior fighting prowess: in other words, of material and human factors. The latter is measured in seamanship, gunnery, and the myriad of traits that set one navy apart from others. Mariners hone these traits not by sitting in port and polishing their equipment but by going to sea. JMSDF flotillas ply Asian waters continually, operating solo or with other navies. The PLA Navy is inert by comparison. With the exception of a counter-piracy deployment to the Gulf of Aden that began in 2009, Chinese fleets emerge only for brief cruises or exercises, leaving crews little time to develop an operating rhythm, learn their profession, or build healthy habits. The human edge goes to Japan.

　　And three, it's misleading to reduce the problem solely to fleets. There will be no purely fleet-on-fleet engagement in Northeast Asia. Geography situated the two Asian titans close to each other: their landmasses, including outlying islands, are unsinkable aircraft carriers and missile firing platforms. Suitably armed and fortified, land-based sites constitute formidable implements of sea power. So we need to factor in both countries' land-based firepower.

　　Japan forms the northern arc of the first island chain that envelops the Asian coastline, forming the eastern frontier of the Yellow and East China seas. No island between the Tsushima Strait (which separates Japan from Korea) and Taiwan lies more than 500 miles off China's coast. Most, including the Senkakus/Diaoyus, are far closer. Within these cramped waters, any likely battleground would fall within range of shore-based firepower. Both militaries field tactical aircraft that boast the combat radius to strike throughout the Yellow and East China seas and into the Western Pacific. Both possess shore-fired anti-ship cruise missiles (ASCMs) and can add their hitting power to the mix.

　　There are some asymmetries, however. PLA conventional ballistic missiles can strike at land sites throughout Asia, putting Japanese assets at risk before they ever leave port or take to the sky. And China's Second Artillery Corps, or missile force, has reportedly fielded anti-ship ballistic missiles (ASBMs) able to strike at moving ships at sea from the mainland. With a range estimated at more than 900 miles, the ASBM could strike anywhere in the China seas, at seaports throughout the Japanese islands, and far beyond.

　　Consider the Senkakus, the hardest assets to defend from the Japanese standpoint. They lie near the southwestern tip of the Ryukyu chain, closer to Taiwan than to Okinawa or Japan's major islands. Defending them from distant bases would be difficult. But if Japan forward-deployed Type 88 ASCMs -- mobile, easily transportable anti-ship weapons -- and missile crews to the islets and to neighboring islands in the Ryukyu chain, its ground troops could generate overlapping fields of fire that would convert nearby seas into no-go zones for Chinese shipping. Once dug in, they would be tough to dislodge, even for determined Chinese rocketeers and airmen.

　　Whoever forges sea, land, and air forces into the sharpest weapon of sea combat stands a good chance of prevailing. That could be Japan if its political and military leaders think creatively, procure the right hardware, and arrange it on the map for maximum effect. After all, Japan doesn't need to defeat China's military in order to win a showdown at sea, because it already holds the contested real estate; all it needs to do is deny China access. If Northeast Asian seas became a no-man's land but Japanese forces hung on, the political victory would be Tokyo's.

　　Japan also enjoys the luxury of concentrating its forces at home, whereas the PLA Navy is dispersed into three fleets spread along China's lengthy coastline. Chinese commanders face a dilemma: If they concentrate forces to amass numerical superiority during hostilities with Japan, they risk leaving other interests uncovered. It would hazardous for Beijing to leave, say, the South China Sea unguarded during a conflict in the northeast.

　　And finally, Chinese leaders would be forced to consider how far a marine war would set back their sea-power project. China has staked its economic and diplomatic future in large part on a powerful oceangoing navy. In December 2006, President Hu Jintao ordered PLA commanders to construct "a powerful people's navy" that could defend the nation's maritime lifelines -- in particular sea lanes that connect Indian Ocean energy exporters with users in China -- "at any time." That takes lots of ships. If it lost much of the fleet in a Sino-Japanese clash -- even in a winning effort -- Beijing could see its momentum toward world-power status reversed in an afternoon.

　　Here's hoping China's political and military leaders understand all this. If so, the Great Sino-Japanese Naval War of 2012 won't be happening outside these pages