When Donald Trump hosted Sanae Takaichi, the Japanese prime minister, last month, he could not resist a gratuitous reference to Pearl Harbor. The US president is impelled to trash longstanding alliances. He has done more than anyone to demolish the postwar global order.

This week alone, the Polish president, Donald Tusk, questioned whether the US would be “loyal” to Nato if Russia attacked. A Pentagon memo reportedly floated suspending Spain from Nato and reviewing support for the British claim to sovereignty over the Falkland Islands. And a report said US officials believe that it has depleted munitions so rapidly in Iran as to put in question contingency plans to defend Taiwan against a Chinese invasion in the near future.

But the outlines of the new world being built in response to authoritarian menace and US unpredictability also came a little more clearly into view. Two major powers are shaking off postwar restraints. Germany published its first military strategy since the end of the second world war – laying out the context for its vast rearmament and recruitment plans. While the country says it is taking on more responsibility within Nato, it is also setting out its national interests more distinctly.

Nato was famously intended “to keep the Americans in, the Russians out, and the Germans down”. With the US threatening exit and Russia knocking at the door, other members are mostly urging Germany upwards – even if the popularity of Alternative für Deutschland, and its sympathy for Moscow, may give some pause for thought. But there are concerns at home and abroad around the politics and economics of this shift. Defence will always be the most sensitive part of pooling sovereignty – and defence industries gain lobbying power at times of economic stress. This week France and Germany yet again failed to resolve differences over the Future Combat Air System joint fighter jet project, announced shortly after Mr Trump first took office.

Meanwhile, Japan relaxed its export rules for lethal weapons. Many saw that as a direct challenge to its postwar pacifism. Conservatives have long wanted the 1947 constitution to be revised and Ms Takaichi has seen her opportunity. Whatever happens on paper, Japan is already becoming more like a normal military power, committed to doubling its arms spending to 2% by 2027.

Major recent protests demonstrate deep domestic concern at a shift away from pacifism, including from fear that Japan may be drawn into US wars. Greater anger comes from China and South Korea, where many believe Japan has never sincerely or sufficiently atoned for wartime atrocities. Yet Ms Takaichi and her South Korean counterpart Lee Jae Myung have, perhaps against expectation, continued a bilateral thaw. Both countries are heavily dependent on the US for security; both are anxiously watching China’s growing might and forcefulness, and a North Korea which is fast expanding its nuclear capacity and working more closely with Russia.

As the second world war reaches the peripheries of living memory, the fear of new conflict looms. And as Mr Trump hammers relationships, others are seeking to strengthen partnerships near and far: visiting Tokyo and Seoul last week, Mr Tusk described South Korea as Poland’s most important ally after the US. Politicians know that security must be built on diplomacy as well as defence budgets. But acting on that insight, perhaps especially with neighbours, can prove tougher.

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