TWO QUESTIONS invariably come up when my colleagues and I speak to Naval War College or Surface Warfare Officers School students about Asian affairs. Why Taiwan? Why should America send fighting men and women in harm’s way to defend it? Many naval officers view the U.S. goal in the Taiwan Strait — prolonging the standoff until China and Taiwan can settle their differences — as insufficient cause for a showdown against the increasingly potent Chinese navy.

I put these questions to Ma Ying-jeou, Taiwan’s newly elected president, during a recent meeting at the Presidential Palace.

This wasn’t my way of playing gotcha with President Ma, whom I like and respect. And to be fair, our delegation, in Taipei for National Chengchi University’s annual Conference on Contemporary China, had only a bit over an hour with him. Elected officials are busy people. Ma’s hectic schedule kept him from fully explaining Taiwan’s value to the United States. Even so, his reply was a bit unsettling, with a strong whiff of wishful thinking about it.

“Everything has changed,” declared Ma. He campaigned on a “Three Noes” platform, meaning no declaration of independence, no unification with the mainland, and no use of force by either side. Former president Chen Shui-bian more or less openly pushed for Taiwanese independence under the guise of constitutional reform. Beijing enacted an “anti-secession” law in 2005, reserving the right to use force should Chen’s “Taiwan independence forces” plunge ahead.

The mercurial Chen’s adventurism could have cost American lives in a war not of America’s making. Chen evidently interpreted President George W. Bush’s 2001 pledge to do “whatever it takes” to defend the island as a blank check to pursue independence under U.S. protection. By refusing to cross this Chinese red line, President Ma has indeed altered the diplomatic and strategic configuration in the Taiwan Strait.

That’s to the good. Assuming the president remains steadfast behind his Three Noes policy, any conflict in the Strait will clearly be a defensive one for Taiwan. Taipei will not drag the United States into war with China through its own recklessness. But that doesn’t address the question of why China would agree to postpone — perhaps permanently — its overriding goal of regaining control of the island. Beijing could seize the initiative should it tire of waiting.

Nor did Ma directly answer the question of why Taiwan matters.

Let’s fill in some of the blanks. Taiwan matters to the United States in large part because it matters to China, whose ideological appeal is in steep decline. The communist regime in Beijing has staked its legitimacy on restoring national unity, reversing China’s century of humiliation at the hands of outside sea powers. Imperial Japan wrung the island from China’s Qing Dynasty following the 1894-95 Sino-Japanese War. In Chinese eyes, recovering it would right a historical wrong.

It’s not all about nationalism, though. Beijing sees Taiwan as an asset critical to its geopolitical aspirations. It occupies the midpoint of the “first island chain,” which roughly parallels the Asian coastline. In 1950, Secretary of State Dean Acheson declared that America’s “defense perimeter of the Pacific” ran along the island chain. This allowed U.S. forces to hem in China at sea while radiating power along the Chinese periphery.

Breaching Acheson’s offshore defense perimeter is a matter of considerable importance for a rising, maritime-minded China.

But Taiwan has offensive uses as well. Gen. Douglas MacArthur once described the island as an “unsinkable aircraft carrier and submarine tender” off the Chinese coast. For MacArthur, it was an instrument of containment. During World War II, Adm. Ernest King pointed to its position athwart important shipping lanes. By wresting Taiwan from Japan, he said, the U.S. Navy could “put the cork in the bottle” of the South China Sea, wreaking havoc with Japanese merchant shipping.

Similarly, bases on Taiwan would extend the Chinese navy’s operational reach seaward, letting Beijing exert a measure of control over sea lanes serving East Asian countries and forward-deployed U.S. naval forces. This would inject a permanent complicating factor not only into U.S. naval movement along the East Asian periphery, but also into U.S. alliance relations with Japan and South Korea, which — like China — depend on seaborne supplies of fuel and raw materials.

Geopolitical logic is clearly one reason Taiwan counts for the United States.

Ideological kinship is another major reason. The concept of a “league of democracies” has been gathering steam for some time now and enjoys backing in both the Obama and McCain campaigns. U.S. policy is agnostic on the final outcome of the cross-strait dispute, insisting only on a nonviolent settlement. Forcible unification, on the other hand, would represent a major setback for liberal regimes everywhere — and would trigger a bipartisan outcry in Washington.

Ideals and interests resonate with Americans. Ma Ying-jeou must factor both into his diplomacy vis-à-vis the United States — lest America conclude Taiwan isn’t worth the potential sacrifice of lives and treasure.

James Holmes is an associate professor of strategy at the Naval War College. The views voiced here are not necessarily those of the Naval War College, the Navy or the Department of Defense.