These are not easy days for America’s allies. From Europe to the Middle East to the Asia-Pacific, security partners of the United States are treading carefully, fearful of antagonizing President Donald Trump, who has cast Washington’s closest allies as freeloaders, slapped them with steep tariffs, and even questioned the sovereignty of some allies with outlandish claims.

Nowhere are the stakes higher than in the Asia-Pacific. The region may appear more stable compared to Europe or the Middle East, but it is anything but placid: a rising China is pressing for greater influence in a region where American primacy—and that of its allies—once went largely unchallenged.

As if to underscore this point, China chose July 6—the day before the NATO summit began in Ankara—to test and fire a long-range ballistic missile from a nuclear submarine, which landed in the South Pacific Nuclear Free Zone. The launch of a missile capable of reaching the continental U.S. drew attention to China’s massive military buildup  and its growing capacity to threaten American cities should Washington come to the aid of regional allies in a conflict with Beijing. The missile test may be a demonstration of China’s new capability, but it is also a reminder of a longstanding threat.

Washington and several U.S. allies in the Asia-Pacific criticized the “irresponsible” test. Still, the episode reinforced allies’ longstanding concerns about the effectiveness and reliability of the U.S. security guarantees to deter an ever more powerful China. What are American allies and partners supposed to do about it? The answers vary across the region, but every answer points toward a stronger American role.

Unease in the Asia-Pacific

There is no equivalent of NATO in Asia. The security arrangements in the region have been based primarily on the hub and spoke system that Washington created after World War II, when it signed alliance treaties with the Philippines, Australia, New Zealand, Japan, South Korea, and Thailand. The U.S. also signed a mutual defense treaty with Taiwan, but it is not an ally the way others are. However, these American allies—the spokes—did not necessarily have defense obligations to each other. All of these countries, to varying degrees, rely on U.S. assurances to deter China from using its military muscle to impose its will on them and the broader region.

Nearly every........

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