Under the Trump administration, U.S.-China relations have moved rapidly and dramatically from a prevailing mood of engagement to one of sharp rivalry. The arena has been primarily economics (trade and investment) as the administration has imposed tariffs on a growing range of Chinese exports to the U.S. and has threatened to extend new tariffs to all Chinese exports to this country. The administration presents a litany of complaints about Chinese behavior to justify these measures ranging from the theft of intellectual property to the manipulation of currency values. The Chinese government has cried foul, declared the tariffs to be a violation of international law, and has promised to respond in kind. In some respects, it is surprising that this change in the tone and tenor of U.S. relations with China has not come sooner. Chinese power and ambitions have been growing spectacularly, and by their own statements, it is clear that China’s leaders envision a 21st century Middle Kingdom soon displacing the U.S. as the world’s dominant superpower. As that realization has grown, it is no surprise that attitudes in Washington have hardened.

Until very recently, the deep and multifaceted economic relationship between China and the U.S. has been seen as “ballast” that would ensure that relations never descended into outright hostility. The familiar argument is that two countries with a combined trade worth more than $640 billion annually are simply too intertwined to let tensions in other areas get out of hand. Those tensions certainly exist as the U.S. and Chinese navies jockey for position in the Western Pacific. The South China Sea, in particular, has become a dangerous point of friction as China tries to enforce a historically and legally bogus claim to ownership of that entire maritime domain.

And there has always been another issue that has long posed a real risk of military confrontation: the status of Taiwan. Situated off the Chinese coast, Taiwan has a long history of obscure and changing ties to China. The truth is that Chinese imperial dynasties seldom took any serious interest in the island and often exerted no effective control over it. Between 1895 and World War II, Japan ruled there. The island generated international attention when Mao Zedong’s communist forces overthrew the government of Chiang Kai-shek in 1949 and the retreating Kuomintang forces fled to Taiwan to make a last stand. Mao’s plan to pursue them and invade Taiwan were derailed by the advent of the Korean War and the Truman administration’s decision to deploy naval forces to prevent a communist attack across the Taiwan Strait.

This left the U.S. in the somewhat awkward position of continuing to recognize Chiang’s anti-communist regime as the lawful government of China and treat the new People’s Republic as an illegitimate pariah. Tensions across the Taiwan Strait remained high as Chinese forces repeatedly threatened to attack Taiwan and U.S. naval deployments stood in their way. All this ended with President Richard Nixon’s famous trip to China and his decision to switch U.S. diplomatic recognition from Taipei to Beijing. When Nixon and Henry Kissinger met with Mao and Zhou Enlai, the thorniest issue was the status of Taiwan. Mao and Zhou insisted that Taiwan must be “returned” to Chinese control. Nixon and Kissinger refused to go that far; Taiwan had too much political support in Congress for the U.S. simply to abandon it. The impasse was broken with an artful formulation by which China and the U.S. agreed that Taiwan was part of China (“the One China policy”) but the U.S. insisted that any reintegration of Taiwan into China must occur peacefully. In the interim, the U.S. retained the right to supply “defensive” military equipment to the Taiwan regime. Nixon fully expected that China would gain control over Taiwan in time and that was a necessary price if China was to become a moderate, responsible great power.

Since the signing of the Shanghai Communique, China has remained implacably determined to bring Taiwan under Beijing’s control. China’s leaders have repeatedly asserted that any attempt by Taiwan authorities to assert sovereign independence for the island would be a red line and the trigger for a military attack. As part of an ongoing effort to pressure and isolate Taiwan, China has systematically pressured the few small nations that continue to extend diplomatic recognition to Taiwan (because of economic benefits) to abandon that policy. The U.S. has typically viewed this diplomatic competition without comment.

For the last two decades, the issue of Taiwan has been relatively quiescent—primarily because Beijing has been convinced that the extensive and growing economic ties between Taiwan and China mean it is just a question of time before Taiwan is once again part of the “motherland.” However, several developments have unsettled that comfortable assumption. First, Taiwan’s vibrant political democracy has made it clear that most Taiwanese, even if they are ethnically Chinese, do not want the island to become a part of China. That same democracy has made it much harder for U.S. leaders to be indifferent concerning Taiwan’s fate. At the same time, China’s growing power has caused a serious rethink in Washington about the Asian security landscape. If Beijing gains control over Taiwan, China’s strategic position will be hugely strengthened—and Japan, for one, will be deeply alarmed. Finally, Nixon’s expectation that a wealthy and powerful China would become more politically moderate has been dashed by Xi Jinping’s reaffirmation of China’s authoritarian communist system.

As part of its economic pressure on China, the Trump administration has begun to signal a rethink of “One China”—going back to a phone call between Trump and the President of Taiwan when the U.S. president-elect did just that. More recently, the State Department has publicly criticized Panama, the Dominican Republic, and El Salvador for diplomatically abandoning Taiwan. Senators have introduced legislation that would authorize the State Department to downgrade relations with any country that derecognizes Taiwan in favor of China. Last month, the State Department formally requested that the Pentagon assign Marine Guards to staff America’s proto-embassy in Taiwan. Earlier this year, Congress passed and the President signed the Taiwan Travel Act that “encourages visits between officials of the United States and Taiwan at all levels.”

It does not require great strategic acumen to suggest that for the first time since the 1950s, Taiwan may move to center stage in the contest for the future of Asia.