Japanese Prime Minister Shinzo Abe ^[1]’s unexpected resignation ^[2] last month for health reasons has raised many questions about the legacy of the country’s longest-serving premier. One of them is whether his successor, Yoshihide Suga, will be able to continue Abe’s geopolitical balancing act as tensions between China and the United States are continuing to escalate dangerously ^[3].

The US and China are critical to Japan’s peace and prosperity. America is Japan’s security guarantor and second-largest trading partner ^[4], while China is its largest trading partner and a next-door neighbour. After Abe returned as prime minister in December 2012, he adroitly managed Japan’s relationships with both.

Abe went out of his way to befriend US President Donald Trump, even as Trump claimed that US–Japanese trade was ‘not fair and open ^[5]’ and demanded ^[6] that Japan quadruple its contribution to the cost of keeping American troops in the country. He further pleased the Trump administration by quietly banning ^[7] the Chinese telecommunications giant Huawei from participating in building Japan’s 5G network.

At the same time, Abe also cultivated ties with Chinese President Xi Jinping, and made a diplomatic ice-breaking trip to Beijing in October 2018 for the first Sino-Japanese summit in seven years. With US–China relations in freefall, Xi seized Abe’s olive branch and planned a state visit to Japan in April, which would have been the first by a Chinese leader since 2008. (The visit has been postponed indefinitely because of the Covid-19 pandemic.)

But Suga will find it increasingly difficult to avoid taking sides in the intensifying US–China conflict. In the short term, he will have to make a decision regarding Xi’s postponed state visit. Opposition to the visit runs high ^[8] within Suga’s Liberal Democratic Party, owing to the Chinese government’s recent imposition of a harsh national security law ^[9] in Hong Kong. A made-for-TV state visit to Japan would be a huge win for Xi, who is eager to demonstrate that the Trump administration’s containment of China is failing.

Chinese pressure to reschedule the visit will put Suga in a bind. Acceding to China’s wishes would cost him political capital at home but scrapping the visit would humiliate Xi and hurt Sino-Japanese ties. The only thing Japan’s new prime minister can do is to find all the excuses he can to continue postponing the visit for as long as possible.

In any case, tensions regarding a largely symbolic Sino-Japanese summit will pale in comparison with the likely impact on Japan of two US–China disputes in the coming years.

First, the US will call on Japan to tighten restrictions on key technologies it supplies to China. But with more than US$38 billion ^[10] invested directly in China and nearly 14,000 firms ^[11] operating there, Japan would find it practically difficult, economically ruinous and diplomatically costly to comply in full with any US sanctions against China.

No one knows how Suga, who was Abe’s cabinet secretary and closest aide for the last eight years, will be able to please the US on the technology issue without angering China, or vice versa. He will certainly face a much harder task than his predecessor, unless the US and China somehow de-escalate their conflict.

Suga will also have a far tougher time sitting on the fence when it comes to security issues. As a member of the so-called Quad—an Indo-Pacific security grouping also including Australia, India and the US—Japan will face US calls to participate in joint naval exercises more often and on a larger scale in order to challenge China’s territorial claims in the South China Sea. Last year, for example, a Japanese aircraft carrier joined US-led naval drills ^[12] in waters claimed by China.

China did not react strongly to Japan’s participation, owing to the two countries’ improving bilateral ties. But it could lash out against Japan if the rapprochement initiated by Abe fizzles and Suga’s administration starts to collaborate with the US more overtly and energetically in disputes over the South China Sea.

One thing that could completely wreck Sino-Japanese ties in the next few years would be the deployment of medium-range US missiles on Japanese soil. Pentagon strategists are eager to position powerful offensive weapons closer to the Chinese mainland, and Japan is an ideal location.

The missiles are still in development, so there is no need yet for the US to ask Japan to host them. But once America has produced sufficient quantities, it is hard to imagine that it will not press Japan for permission to deploy them. Were Japan to agree, its relations with China could face their worst crisis since the two countries restored diplomatic ties in 1972.

Of course, none of these troubles are Abe’s or Suga’s fault. But they illustrate once again the plight of a country squeezed between two duelling geopolitical giants—and the scale of the diplomatic challenge facing Japan’s new prime minister.