The Taiwan Strait has enjoyed relative peace for the last five decades, thanks largely to the American policy of “strategic ambiguity,” which deliberately leaves open the question of what the U.S. would do if Taiwan were attacked. China, wary of American intervention, has held off on invading, while Taiwan, wary of American abandonment, has held off on declaring formal independence. The policy has thus far forestalled catastrophe and remains the U.S.'s best shot at preserving the fragile peace.

Not everyone is convinced, however. Dr. Jennifer Kavanagh argues in these pages that strategic ambiguity is “neither sustainable nor wise for America” and urges Washington to publicly refuse to defend Taiwan. That would be a grave mistake. Dismantling Washington's proven approach to managing cross-strait tensions and, worse, abandoning a longstanding democratic partner would weaken deterrence, invite further Chinese intimidation of U.S. allies, and imperil America's economic lifeline.

>>> America Is Sailing Through the Taiwan Strait Less. Does It Matter?

To start, Dr. Kavanagh asserts that strategic ambiguity is outdated because when the U.S. adopted the policy in 1979, “China's military was no match for that of the U.S.” Today, she argues, China's military is growing so quickly that America's ability to outlast it in a war over Taiwan “is now in question.”

But that misreads why strategic ambiguity works. China is undeniably more powerful now, yet deterrence does not hinge solely on military success. Beijing also weighs the price of a costly win, and Chinese President Xi Jinping's calls for a “strategic decisive victory” show that he wants a quick, clean win, not a grinding war. Although America's military edge over China has narrowed in recent years, U.S. forces can still exact a punishing toll.

Further, Dr. Kavanagh surmises that China, having taken Taiwan, would not use it as a “launchpad for further expansion.” Consider, however, Beijing's recent behavior in the South China Sea. Satellite imagery has exposed China's efforts to militarize features by building ports and airstrips. From these locations, Beijing continues to aggressively—and sometimes violently—harass Southeast Asian nations, leading to heightened clashes. There is little reason, then, to believe that China would not use the island as a foothold to menace Japan and the Philippines over disputed territories.

>>> China Is Moving Toward a New Form of Coercion at Sea

Finally, Dr. Kavanagh says that unification between China and Taiwan does not “threaten U.S. existential interests.” This view is divorced from reality. Taiwan sits astride the world's most important sea-lanes, through which the lion's share of global commerce flows. Control over Taiwan positions China to weaponize access to supply routes which could imperil the U.S. economy.

The U.S. also remains incredibly dependent on Taiwanese semiconductors. Reshoring semiconductor manufacturing, as Dr. Kavanagh proposes, will be difficult, and any hurried attempt to do so may substantially raise costs for American consumers. For the foreseeable future, Taiwan remains the best location for production, leaving the chip supply at Beijing's mercy should the island fall. If China seizes Taiwan and cuts off access, it could shrink the U.S. economy by $2.5 trillion and plunge the country into the worst recession in recorded history.

Strategic ambiguity is an imperfect tool, but by keeping both Beijing and Taipei guessing, it has helped protect the peace in the Taiwan Strait. Dr. Kavanagh's proposal would not only end that carefully cultivated uncertainty but also strip away the restraint it has long compelled.