On Friday, Japanese Prime Minister Shinzō Abe will make an historic visit to Darwin, seventy-six years after the first attack by a foreign nation on post-settlement Australia. In February 1942, about 240 Japanese aircraft conducted two raids on the city, killing at least 235 people and prompting half of the population to flee south.

Abe’s trip will mark more than a reconciliation. It caps off a turnaround in the relationship between these two countries: from enemies, to trading partners, and now to their defence and diplomatic embrace. As China rises, and Asia’s power balance changes, and Donald Trump disrupts traditional alliances, Australia and Japan are finding that their interests in the region all but overlap.

Accompanied by Scott Morrison, Abe is expected in Darwin to pay respects to the Australian and Japanese war dead. He will also inspect the $54 billion Ichthys gas project, Japan’s largest-ever foreign investment.

In this morning’s announcement of Abe’s trip, Morrison said the Australia–Japan relationship was “one of immense progress and opportunity”.

“Prime Minister Abe’s visit is deeply symbolic and significant and it will build on our two countries’ strong and enduring friendship,” he said.

Significantly, the two leaders are likely to discuss a new defence deal that will enable more military exercises and troop visits.

This agreement will continue the post-war trend of gradually strengthening bonds: in 1957 the two countries reached a landmark deal to normalise trade ties, and in 1976 they signed a pact to broaden cultural ties. For decades, the relationship was dominated by commerce, as Japan became Australia’s largest trading partner – a position it held for almost thirty years until it was replaced by China.

But recently the countries have increasingly shifted their focus to defence ties. In 2007, they signed a joint security deal, and this year or next are likely to sign an agreement that could – in a reversal of history – facilitate peaceful dispatches of Japanese troops to train in Australia.

The push for closer defence ties partly reflects Abe’s attempt to steer Japan away from its self-imposed constraints after World War II and to revise the country’s United States–drafted pacifist constitution.

However, the shift is also a consequence – and barometer – of recent changes in the region.

Both nations found prosperity in an Asia in which the power of the United States was unrivalled, a condition that guaranteed stability and free trade flows and allowed them to avoid excessive military spending. Now, Washington’s primacy is ending – and neither nation wants China to entirely fill the vacuum.

But the two countries have also discovered that their shared vision for the region is no longer identical to that of the United States. Both countries have been backing a free trade system in which China is not at the centre. But this is no longer the goal of Washington, which supports the blow to Beijing but is suddenly cautious about free trade. Both Trump and Hillary Clinton opposed the Trans-Pacific Partnership, a twelve-nation trade deal which, significantly, excluded China. After Trump pulled out – his first executive action – the agreement was renamed the TPP-11, and Australia and Japan (along with Canada) have been its main champions.

Trump’s idiosyncratic approach to foreign policy is also bringing Australia and Japan closer. His presidency has left Tokyo nervous. During his 2016 election campaign, he suggested the stationing of US troops in Japan was too expensive and that Japan should consider developing its own nuclear weapons. Trump has not followed through with his threat to make Japan cover the costs of the troop deployment but has targeted Japan with trade tariffs. He also failed to consult with Tokyo as he embarked on negotiations with North Korea, just months after it flew test missiles over Japan.

Not surprisingly, Abe is seeking new partners. Last month, he travelled to China, the first official visit by a Japanese leader in seven years. Days later, he welcomed India’s prime minister, Narendra Modi, to Japan to enhance defence and diplomatic ties.

Abe can no longer count on the old post-war certainties of Asia. Nobody can. The relationship between Australia and Japan is no longer simply transactional. These two countries, bookends of Asia, will increasingly need to do their own work to shape the order around them, because their closest ally may no longer be willing to do it for them.