The territorial dispute in the South China Sea is building towards a flash point. There is a persistent idea that it's about nothing more than tiny islands and useless reefs.
If that's all it is, then it's not worth a big argument between the US and China. And it's certainly not worth risking a war between the world's two biggest powers, most reasonable people would agree.
China has built land area of about 800 hectares, all reclaimed from the ocean, in the last year and a half, on atolls that are also claimed by other countries in the region – the Philippines, Vietnam, Malaysia and Brunei.
Beijing is building airstrips and ports to "militarise" the islands, according to the US.
The US President, Barack Obama, complained in April that China was using its "sheer size and muscle to force countries into subordinate positions".
China didn't pay any heed. It said that it was within its sovereign rights and the reclamation proceeded apace, with hundreds of ships dredging and building. The US decided to press the point that it would not accept any intrusion into international air space.
It sent military aircraft to fly over some of the islands last week. China's navy ordered the Americans to leave the area immediately. They did not. China protested angrily but didn't shoot.
Australia's Defence Secretary, Dennis Richardson, said last week: "It is legitimate to ask the purpose of the land reclamation – tourism appears unlikely."
And then, on the weekend, a Chinese admiral explained the purpose. He said the land reclamation projects, a thousand kilometres from China's coast, are not a land grab but intended for "international public services".
Sun Jianguo listed disaster relief, maritime search and rescue and scientific research as the benefits it could offer.
But still the pressure builds. The US plans to sail and fly past and over the atolls to assert freedom of navigation. Washington says it is offering $US425 million to the south-east Asian claimants to beef up their navies and coastguards.
On the Chinese side, Beijing says it reserves the right to declare an Air Defence Identification Zone over the area.
This would mean that any aircraft would need to identify themselves before entering the airspace or risk being shot down.
"This has the potential to escalate into one of the deadliest conflicts of our time, if not history," said Malaysia's Defence Minister, Hishammuddin Hussein, on the weekend.
Have the Americans taken leave of their senses? Is this shaping as another Iraq invasion a la 2003, a concocted excuse for a pointless war? In truth, the reason that China and the US are prepared to escalate this confrontation is that it is about much more than tiny islands and useless reefs.
On a strategic level, it's about control of the world's busiest shipping route. China is laying claim to 90 per cent of the South China Sea.
About half the world's commercial shipping passes through the area, including 60 per cent of Australia's exports.
On a geological level, it's about some of the world's most prospective seabed oil and gas deposits.
On a military level, it's about China's avid desire to push the US navy away from its coast. Beijing craves uncontested domain over its maritime approaches.
The US Seventh Fleet has been unchallenged ruler of the Pacific since World War Two. A fast-rising China is now challenging.
And on the level of global governance, it's about whether there are any rules governing countries, or whether a country can get its way through use of force.
And we know that China isn't really building a string of islands just to be nice to other countries in the region.
If China cared about their interests, it wouldn't be riding roughshod over their claims.
China routinely dismisses critics by saying that it is negotiating a code of conduct with the South East Asian claimants, and everyone else should butt out.
But Beijing first agreed to negotiate a code of conduct with ASEAN in 2006. And what's happened?
"There's been no sign of progress for nearly 10 years," observes Alan Dupont, a professor of international security at NSW University. "They can't even agree on the basis for preliminary principles for negotiating."
As China's Foreign Affairs Minister, Wang Yi, said in 2013, "China believes that there should be no rush." And why would China want to rush?
In the meantime, it's changing the facts on the ground. A prominent Chinese general has described the approach to maritime territorial claims as a "cabbage strategy".
Major General Zhang Zhaozhong, a military theorist with the People's Liberation Army (PLA) National Defence University, has said that China puts down one "cabbage leaf"or layer of territorial assertion over another. First might be ships of the fishing administration, then maritime surveillance vessels, then the Chinese navy. Adding extra layers, such as air defence zones or new bases, is consistent with this way of patiently building a thickening circle of claim by force.
All that's happened in recent weeks is that the US has decided that it can't stand by and allow China to dominate the entire region against the will of its smaller neighbours and endanger international right of way.
The US position, which is also Australia's position, is that it doesn't take sides in the argument over territory, simply that it wants them settled by negotiation and not force.
The good news is that China's creeping invasion of the region is now being openly challenged for the first time by a country with the power to do something about it.
The bad news is that there is no solution in sight.
Peter Hartcher is international editor. SMH