American planners once traced east-west lines of coaling stations in the Pacific to reach China and Japan. But the second world war changed their perspective, says Michael Green of the United States Study Centre in Sydney. The attack on Pearl Harbour showed that vast distances do not guarantee safety; America’s island-hopping campaign highlighted the importance of north-south axes. Later on, the first island chain helped America contain the Soviet Union. Now it holds back China.

To see how, begin with the northernmost link, Japan. Despite its pacifism, it is greatly boosting defence spending. American marines in Okinawa are practising how to scatter and defend the islands and sea passages. The next link, Taiwan, is under intense strain, given China’s aim to retake the self-governing island by force if necessary. America may soon announce the first “drawdown” of weapons from its own arsenal, pre-emptively strengthening Taiwan much as it has armed Ukraine. The Philippines, the next link, is weaker but has agreed to give America access to nine bases in the country; in return America is helping to beef up its forces.

In the second chain, meanwhile, America is devising ways to disperse its jets in wartime and hardening the defences of Guam. It wants to project more power from Australia, where it rotates air force and marine units. It is working with Britain to supply nuclear-powered submarines to Australia under the AUKUS deal; the three are also working on new weapons, including hypersonic missiles. Farther afield, the Quad—America, Australia and Japan working with India—is not a formal security grouping, but their navies exercise together. Across the region, American-led war-games are becoming bigger and more sophisticated. Sometimes America’s security arrangements are limited, for instance its new defence deal with Papua New Guinea; or its efforts to help littoral states improve “maritime domain awareness” to, say, curb illegal fishing by Chinese fleets. This, too, helps enmesh America in the region.

Travelling across Asia on an E4-B, the flying command post of Lloyd Austin, America’s defence secretary, brings alive this web-weaving strategy. One expected highlight turned to disappointment when the Chinese defence minister, Li Shangfu, declined to meet him at a talkfest in Singapore—even as a near-collision of American and Chinese warships in the Taiwan Strait on June 3rd made plain the need for such contacts. (Antony Blinken, America’s secretary of state, is visiting on June 18th).