A leading foreign policy scholar once described alliances as “transmission belts for war,” mechanisms for converting local conflicts into far wider and more destructive wars.  We now have a graphic example of that danger in the U.S. security treaty with Japan.

Tokyo is embroiled in an emotional territorial dispute with Beijing over a chain of uninhabited rocks in the East China Sea, which Japanese call the Senkaku Islands and Chinese call the Diaoyu Islands.  Although Japan administers those islands, Beijing insists that both maritime precedent and history confirm that the territory is rightfully part of China.

That dispute has existed for decades, but tensions have been escalating over the past two years, and have now spiked dramatically.  Late last week, Xinhua, the official Chinese news agency, published a map of a newly established East China Sea Air Defense Identification Zone, which includes the airspace over most of that body of water—including the disputed islands. China’s Defense Ministry also released identification rules for aircraft in the zone and stated that “China’s armed forces will adopt emergency measures to respond to aircraft” that don’t abide by those rules.  Over the weekend, the Chinese air force began patrols to emphasize the point.

It was hardly a surprise that Japan did not respond well to Beijing’s proclamation.  A Japanese Foreign Ministry spokesman stated bluntly that the islands were part of Japan and that Beijing’s actions were an unacceptable attempt to change the status quo.  The move was “very dangerous” and could lead to unforeseen, but clearly undesirable, outcomes.

A nasty spat between Asia’s two strongest powers, and the countries with the world’s second and third largest economies, is obviously troubling.  But Washington did not help matters by weighing-in immediately on behalf of its Japanese ally.  Secretary of State John Kerry not only admonished China to exercise restraint, but emphasized that the United States was “steadfastly committed to our allies and partners.” Officials provided pointed reminders of Washington’s position that the U.S.-Japan security treaty covers the Senkaku Islands.  Secretary of Defense Chuck Hagel rebuked China for “a destabilizing attempt to alter the status quo in the region.”

There are a couple of worrisome aspects about the U.S. position.  First, although China’s actions are needlessly provocative, Beijing is not the only party to disrupt the status quo.  The Japanese government’s decision last year to nationalize the islands from private owners certainly did so.  Yet U.S. officials had little to say about that move.  Second, Washington’s stance on the underlying territorial dispute is contradictory, if not disingenuous.  U.S. leaders simultaneously insist that they do not prejudge the resolution of the territorial matter and emphasize that the security treaty covers the islands.  But the treaty applies to the islands only if the United States regards them as Japanese territory.  That position definitely prejudges the issue.

Although Japan should be strong enough to defend its own security and national interests without U.S. involvement, one can make the case that protecting Japan and helping to keep it out of Beijing’s orbit is also a legitimate interest of the United States.  Whether it is important enough to risk war with China is a much more difficult question, but it is folly to risk such a war merely to back an ally in a murky territorial dispute over some uninhabited rocks.  Yet that is a danger we now incur.

This episode is a textbook example of why the United States should use only informal security arrangements, not written, long-term treaties.  The former approach gives Washington far greater flexibility regarding the best response to changing conditions.  History will not be kind to U.S. leaders if a security treaty causes this country to end up in a military confrontation with China over such meager stakes as the Senkaku/Diaoyu Islands.