This alliance is about protecting Taiwan, but trade has complicated old tensions

‘Australia’s government has firmly nailed the Southern Cross to the American mast’

‘Whether Britain would really be willing to get dragged into a war with China is as ambiguous as ever’

For decades, the focus of security studies in the Western Pacific has been the Taiwan Strait. If China invades Taiwan, the question goes, would the United States come to the island’s defence? And if so, would Britain be drawn into World War Three alongside its ally?

It is an important question, and it was the one Theresa May asked when Boris Johnson announced a new security alliance with the US and Australia designed to contain China. But it also rather misses the point. For the true driver of the Aukus arrangement is an ocean-wide confrontation far more complex than the decades-old tensions between mainland China and its breakaway island province. From Tokyo to Canberra, via Hanoi and Port Moresby, countries are being forced to take sides in what diplomats still do not want to call a Cold War.

For years, Canberra tried to balance its strategic alliance with the US with its blossoming trade partnership with China. Recent trade disputes have made that stance difficult to maintain.

Scott Morrison, the Australian prime minister, publicly came off the fence in June when he warned fellow Western leaders at the G7 summit in Cornwall of “growing instability in the Indopacific that in turn is threatening broader global stability”.

With the decision to buy nuclear submarines, his government has firmly nailed the Southern Cross to the American mast.

Australian officials still insist they are continuing to balance the two relationships, pointing to strong economic common interests with China that have survived recent quarrels. But such ambiguities cannot disguise the contest unfolding across the Western Pacific.

Besides Taiwan, China’s expanded navy is engaged in disputes with the Philippines, Vietnam and Japan over reefs, shoals and uninhabited islands in the South and East China Sea.

To allow it to move freely against any of those potential rivals, it has undertaken the fastest navy ship building programme of modern times. It has also invested in long-range, hyper-sonic weapons.

The new Australian submarine fleet is hardly going to thwart an invasion of Taiwan or the Spratly Islands. But the craft do have a greater range and can remain submerged for greater periods of time than their diesel electric alternatives.

Whether Britain would really be willing to get dragged into a war with China is as ambiguous as ever.

But there has been no comparable build-up of military tensions in the Western Pacific since American, British and Australian warships battled the imperial Japanese navy for control nearly 80 years ago.

Governments on all sides will be hoping this maritime Cold War never turns hot. But that is the fight they are readying for.