Little over a year ago, Japanese premier Shinzo Abe’s biggest worry, as he assiduously courted Donald Trump, was that the US president would do deals with China at the expense of America’s strategic commitment to Japan. As Mr Trump has instead escalated a trade war with Beijing, Tokyo’s concern now is being caught in the middle of a broader Sino-US confrontation. That is the backdrop to Mr Abe’s arrival in China on Thursday for a three-day visit and meetings with president Xi Jinping — the first bilateral visit by a Japanese leader since 2011. It marks an important step in a gradual rapprochement between the world’s second- and third- largest economies.

The warming relations are an unambiguously positive development. Of all the world’s geopolitical hotspots, north-east Asia has perhaps the biggest potential for catastrophe. The combustible mix includes North Korean nuclearisation, South Korean and Chinese historical grievances dating from Japan’s wartime expansion, and China’s promise to conquer Taiwan by force if necessary. Since the 1950s, large garrisons of US troops in Korea and Japan have guaranteed Pax Americana in the region. But Mr Trump has made clear his desire to bring them home, leaving longtime allies to fend for themselves.

Over the past decade, meanwhile, domestic political dynamics and rising nationalism in China and Japan have worsened territorial disputes and deepened the diplomatic stand-off. China has been particularly belligerent in recent years as it attempted to erode Japan’s de facto control of disputed islets in the East China Sea and challenge US regional dominance.