China, under the leadership of strongman Xi Jinping, has become more assertive in East Asia, recently increasing military flights near Taiwan, which it regards as an errant province. Of course, this has spun up the interventionist foreign policy establishment in the United States. For example, Richard Haass, president of the Council on Foreign Relations, recently advocated removing the public ambiguity surrounding whether the United States would defend Taiwan if attacked by China. Yet making this informal alliance an explicit one is an extremely bad idea.

Some allege that Taiwan is strategic to the United States, because in any war with China it would be like having a giant aircraft carrier off the coast of our adversary or because the offshore island is near important trading routes. Although the Chinese want Taiwan reincorporated into China primarily because of domestic nationalist sentiments, their military is probably painfully aware of Taiwan’s potential for use as a large base from which the United States could attack China. This threat is vivid for China, given that it was carved up by Western powers in the late nineteenth and early 20th centuries, including the U.S. contribution of forces to Western military suppression of the anti-colonial Chinese revolt labeled the Boxer Rebellion.

Of course, if the Chinese had the use of bases on Cuba, off the U.S. coast, the United States would not stand for it—as the Cuban Missile Crisis with the Soviet Union during the Cold War showed. As for America protecting sea lanes for trade, China depends heavily on international commerce for economic prosperity and has little incentive to restrict such trade, thus raising the hackles of the entire world.

More important, Taiwan’s value as a base in any U.S. military dust-up with a nuclear-armed China pales in comparison with the role a U.S. defense of the island could play as a cause of that potentially cataclysmic war in the first place. China would have a much easier time attacking Taiwan than the United States would have defending an island halfway across the world. When push comes to shove, China is much nearer to Taiwan than is the United States and feels much more strongly about getting it back than does the United States about protecting it.

Thus, making an explicit U.S. commitment to do so should be avoided. Any significant U.S. armed confrontation with China has the potential to go nuclear, and the United States would need to answer the ultimate question of whether it wants to sacrifice Los Angeles (and other U.S. cities) to save Taipei. The answer should be a resounding, “No!”

The fallback argument for interventionists is the rather imperial one used throughout the Cold War, that “American credibility” with its many other wards around world would be undermined if the United States failed to defend Taiwan. This argument was used to entangle the United States in the Korean and Vietnam Wars, which also were fought over non-strategic areas in the adversary’s sphere of influence.

More generally, in its decades as a superpower, the United States has lost sight that alliances, formal or informal, are not ends in themselves but means to an end: enhanced security for the United States, its people, and its way of life. Alliances that drag countries into needless war do not enhance security, as the Europeans found out in the First World War. Moreover, the United States has declined economically since 1970, all the while wasting resources on defending wealthy nations around the world, including Taiwan. The United States has forgot that economic strength underpins other indices of national power, including military prowess.

Yet all is not lost for Taiwan. Islands have intrinsic security because amphibious assaults across water are one of the most difficult military undertakings, especially in the age of satellite reconnaissance and precision-guided munitions. It has been a long time since a major amphibious assault has been undertaken successfully. Taiwan, as a small nation in the sphere of influence of a major power, can use the porcupine strategy, not aiming to win a war but merely making the damage inflicted on China great enough to discourage an attack. Taiwan already has a good air force that should make China skittish about a vulnerable amphibious attack force of surface ships.

The wealthy island can carry out this strategy by purchasing even more weapons from the United States, including offensive ballistic and cruise missiles. Reluctance by the United States to sell such offensive weapons—to discourage a Taiwan standing behind a U.S. defense shield from provoking a war with China—would melt away after the United States made clear that no such shield for Taiwan would exist in the future. The Taiwanese would be responsible for their own deterrence. This new reality would make Taiwan smarter about the weapons it buys.

Taiwan’s self-defense is far from hopeless, and a debt-ridden United States needs to make clear that it is disentangling from likely futile defenses of non-strategic, far-flung outposts near potentially adversarial nations.