The last time US troops were based in Australia was during the Second World War, when Japan seemed about to invade. Seven decades on, the news that a permanent task force of 2,500 Marines will be based around Darwin in northern Australia is proof of America's determination to contain a less directly threatening but even more dominant power in the Asia-Pacific region.
That power of course is China. This week, during his first visit as President to Australia, Barack Obama maintained that the deployment was not a hostile move, rather a signal of US commitment to regional stability from which everyone, including China, would benefit. But his target was plain. Beijing's increased power brought increased responsibility, he declared: "It is important for them to play by the rules of the road."
In the eyes of many of its neighbours, however, Beijing is not playing by those rules, not least in its military build-up and its aggressive territorial claims in the South China Sea. The only realistic counterweight to China is the US, and unsurprisingly Washington's move has been greeted warmly by US allies in the region but frostily by Beijing.
The shift in America's global priorities is clear – away from debt-paralysed Europe and the Muslim world, where long US wars in Iraq and Afghanistan are winding down, to the emerging new centre of global economic gravity in Asia. It is noteworthy that Mr Obama's next stop after Australia will be Bali, Indonesia, where he will be the first US President to attend an East Asian summit – whose leitmotif, inevitably, will be the growing power of China.
But this deployment also sends a message about Mr Obama himself. Listen to the Republican presidential candidates, and he is a weak-kneed dilettante, far too accommodating to rivals like China and Iran. The truth, if anything, is the opposite. In the war against al-Qa'ida that now seems largely won, he ordered the bold raid that killed Osama bin Laden, and has used controversial armed drones more extensively than his Republican predecessor. The hallmark of the Obama foreign policy is hard-nosed realism. The decision to send a contingent of Marines to Australia is cut from a similar cloth.