Here's a question for the presidential candidates as they prepare for their last debate: How will you approach China—Taiwan relations?

This isn't an abstract question: Our next president could well have to deal with a war in the Taiwan Strait. China is building a commanding military edge over Taiwan at the same time pressure is mounting on Beijing to act against the island. While Sino—American relations have been on the upswing since 9/11, that could change overnight.

Last spring the Taiwanese electorate returned President Chen Shui—bian, an outspoken proponent of independence from the mainland, to office. Chen has vowed to put a new draft constitution to a referendum in 2006, flouting the longstanding "one China" principle. If approved, the document would enter into force in 2008. Beijing interprets the plan to enact a new constitution as a precursor to formal Taiwanese independence.
 
Taipei thus seems to be edging toward one of China's "redlines" for military action. In effect it has imposed a deadline for some kind of diplomatic or military showdown, curtailing China's more leisurely approach to unification.

Alarmed at Chen's plan, Beijing has abandoned its usual circumspection, threatening to use force to compel talks on reunification. China has positioned some 500 short—range ballistic missiles across the Strait to intimidate the island's leadership into opening talks or, failing that, to bludgeon the island into submission.

Beijing has also embarked on a military buildup with the explicit purpose of denying U.S. aircraft carriers access to the Strait. It has bought state—of—the—art diesel attack submarines, surface warships, and anti—ship missiles from Russia. It has also begun to build high—tech armaments of its own, notably a destroyer billed in the official Chinese press as "China Aegis" and a new diesel submarine whose existence only recently became known to the West.

These capabilities are eminently suited to a strategy of sea denial in the waters surrounding Taiwan. China doesn't need to beat the United States Navy in an all—out war. It only needs to establish a local preponderance of force, fending off American reinforcements until it can defeat Taipei —— handing the world the fait accompli of a unified China. "Aircraft Carriers: Suggest You Keep Out of the Taiwan Strait!" advised one article in "Junshi Wenzhai" ("Military Digest").

Meanwhile, Taiwan's mercurial politics has stalled plans to purchase some $18 billion worth of diesel submarines, maritime patrol aircraft, and other arms from the United States. Prospects for a $4 billion sale of Aegis guided—missile destroyers —— ships capable of shooting down the ballistic missiles likely to be lofted Taiwan's way in wartime —— are likewise bleak. Taiwan needs these armaments to sustain the technological edge long enjoyed by its armed forces.

While the Taiwanese bicker among themselves, then, the cross—strait military balance has begun to tip inexorably in Beijing's favor. China is developing military means commensurate with its political ends, giving Beijing a viable military option vis—ﾃ —vis Taiwan. By contrast, Taipei has embarked on an ambitious new policy while allowing its military means to atrophy.

In short, Taiwan must bring its means into sync with its ends or risk suffering the fate of another island nation that, two—and—a—half millennia ago, dared to defy a militarily dominant neighbor. In 416 B.C., a tenuous peace between Athens and Sparta, the two superpowers of the Greek world, began to unravel. The warring powers considered their next move. Athens cast its gaze on the city—state of Melos, which had resisted joining the Athenian Empire.
 
Why target Melos? Because the Athenian empire had not only vital geopolitical interests but its very survival at stake. Operating from the island, the potent Athenian navy could project power along the coasts of Sparta's Peloponnesian redoubt. Athens also wanted to make an example of the Melians, who had defied the imperial will in the past. In so doing, it would deflate independence movements among its restive, war—weary allies.

Athens dispatched ambassadors, accompanied by a powerful expeditionary force, to demand surrender. Then ensued the Melian Dialogue, one of the most remarkable episodes in Thucydides' account of the Peloponnesian War. Several themes from the dialogue are relevant to China—Taiwan relations.
 
First: Questions of justice apply only when there's a rough parity of power between the contending sides. Declared the Athenian ambassadors in language remarkable for its bluntness, "when one side is stronger, it gets as much as it can, and the weak must accept that." The gods had ordained it thus. "Nature always compels gods (we believe) and men (we are certain) to rule over anyone they can control."
 
Rarely has there been a purer statement of realpolitik.
 
Second: A mismatch in power allows the stronger side to pursue an aggressive diplomacy in hopes of winning without fighting (the "supreme excellence" in Chinese statecraft). Observed Yale's Donald Kagan, the Athenians, confident in their stifling naval power, sought to dishearten the Melian Council, and thus to prevail without resort to arms. Hence the harsh, overtly immoral tone of the Athenian pronouncements.
 
Third: Hope is not a strategy. It's risky to count on luck or foreign allies. The Melians held out hope that, since their cause was just, they could trust to fortune or their Spartan kinsmen to avert disaster. "Hope!" sneered the Athenian delegates. "It is a comfort in danger...do not be like the ordinary people who could use human means to save themselves but turn to blind hopes when they are forced to give up their sensible ones."
 
In the end, the Melians opted to fight rather than submit to Athenian blandishments, and the Athenian force invested the city. Once the city fell, the Athenian assembly voted to put the adult males to death and enslave the women and children.
 
What of Taiwan? The Melian example suggests Beijing, mindful of its own vital interests, will take an even more assertive line as the cross—strait military balance shifts in its favor. Beijing has a geopolitical interest in wresting the island from its inhabitants: Taiwan would make an invaluable naval base, shifting China's defense perimeter seaward. Reunifying the motherland would discourage independence movements in Tibet and Xinjiang, consolidating Beijing's rule.

Taipei has a choice. It must bring its military means in line with its political aspirations. It can do that by scaling back Chen's plans for outright independence, thus backing away from Beijing's redlines for war. The uneasy status quo in cross—strait relations would resume. Or it can continue down the path to independence, realizing that China may, in the not—too—distant future, opt to break the impasse by force.

For its part, Washington needs to do three things. First, it should reaffirm that it will stand by its traditional policy of helping Taiwan maintain its de facto independence. Second, it should make clear that the United States has not issued the island a blank check to pursue de jure independence. The kind of brinksmanship Chen Shui—bian has pursued could end up getting Americans killed.

The American security guarantee is not and cannot be unconditional. The United States cannot afford to tie its vital interests to decisions reached in Taipei.

In either case, Taipei needs to stop putting off defense modernization. It can build up military power sufficient to show China that military force isn't the answer to the cross—strait stalemate. Or it can continue to let its armed forces decay——and hope it doesn't go the way of Melos.

James R. Holmes, Ph.D. is Senior Research Associate, Center for International Trade and Security School of Public and International Affairs, University of Georgia