WHEN Japan's Prime Minister Shinzo Abe went to Washington last week, he desperately wanted US President Barack Obama to give him an ironclad, public assurance that America would support Japan against China over the disputed Senkaku/Diaoyu islands - if necessary with armed force.
He did not get it. Mr Obama did not mention the issue in their very brief appearance together, and US statements seemed to step back from the cautious but firm warning issued to China by former secretary of state Hillary Clinton just a few weeks ago.
Mr Abe put a brave face on all this, giving a feisty speech in which he declared that "Japan is back". But the visit only highlighted the intense dilemma Japan now faces in managing its alliance with Washington, as Beijing grows more powerful and pushier.
We can understand why Washington wants to avoid inflammatory language which might only increase the risk of being drawn into a conflict with China over some worthless rocks. But it is important to look at this from Tokyo's perspective too.
For Tokyo, the steadily escalating tension with China over the disputed islands is about much more than uninhabited rocks. The dispute confronts Japan with the full implications of Asia's rapidly shifting power balance, revealing fundamental changes in Japan's strategic situation which carry immense implications both for Japan itself and for its neighbours in Asia.
These changes erode the whole basis of the carefully nurtured post-war strategic alignment with America which has served Japan so well, and confront it with some very frightening choices about what to do.
For almost 70 years, even as it became an economic giant, Japan's strategic policy has been defined by its willing dependence on American protection as the foundation of its security. But dependence on America has only worked so well and lasted so long because Japan has always been reasonably sure that America would be willing and able to stand up for Japan against any threat.
Now, however, that confidence is waning because of China. The richer and stronger and more assertive China becomes, the more Japan worries about China, and the less confident Japan can be that America will always be there to help.
On the one hand, Tokyo naturally fears that as China's power grows, it will increasingly try to force Japan to accept a subordinate place in a new Asian strategic and political order under China's thumb.
On the other hand, Tokyo perfectly understands that the stakes with Beijing are growing for Washington too. China is vital to the United States as an economic partner, so the cost of any rupture with Beijing has become almost incalculable. At the same time, the People's Liberation Army's growing air and naval capabilities have increased the risks of any armed clash with China, and made it more likely that any minor skirmish would escalate into a major conflict.
Gone are the days when America could force China to back down simply by sending an aircraft carrier to show the flag, with little or no chance of serious fighting. America today worries that any armed confrontation with China could spiral into an economic and military maelstrom and perhaps even a nuclear exchange.
Japan's leaders know that these pressures inevitably raise the threshold for US intervention to support Japan against China, and thus also raise Japan's anxieties about being abandoned by its ally.
Now these fears seem to be coming true over the island dispute. Japan desperately needs US support to resist China's bullying, and worries that it will have to back down if America does not step up when push comes to shove. For Tokyo, that would set a terrifying precedent, virtually acknowledging China's primacy and Japan's subordination.
Japan realises that America will not confront China unless the US feels its own direct interests are threatened, as well as Japan's. In other words, the more Washington sees Beijing as a rival in a zero-sum competition for influence in Asia, the more confident Tokyo will be of US help, and the more secure it will feel. But at the same time, escalating rivalry between Washington and Beijing poses immense risks for Tokyo as well.
Here lies the dilemma at the heart of Tokyo's strategic predicament today. The sharper the rivalry between the US and China, the more confident Japan can be of US support. But at the same time, US-China hostility is a disaster for Japan because, like everyone else in Asia, it depends on these two giants getting on well if it is to live in peace and prosperity.
Japan's dilemma has grave implications for the rest of Asia as well. As long as Japan feels safer when the US and China are rivals, it will tend to discourage Washington from building the kind of stable and trusting relationship with Beijing which is essential if Asia is to remain at peace. And because Japan is so important to the US in Asia, its views will have a lot of influence on the way Americans think about China. So Japan's fears may destabilise the whole of Asia if they prevent America and China from finding a way to get along.
How can Japan escape this dilemma? The answer is simple, but far from easy. Japan's problem arises from its dependence on the US for protection from China, so the solution is to cease that dependence and re-emerge again as an independent great power able to look after its own security.
That idea raises lots of hard questions. First, does Japan have the capacity to do this? It clearly does in terms of material power. Despite its problems, Japan remains an immensely wealthy country with huge industrial and technological capacities, and formidable military forces. It could stand up to China on its own if it wants to.
Whether it has the political will to make such a radical change to its post-war strategic posture is less clear. Certainly it would take much bolder action than Japan's sclerotic governments have shown for a long time, but that is not out of the question. Certainly the debate in Japan about strategic questions has opened up a lot over the past few years, and Mr Abe's success in the recent elections itself is a sign of how worried the voters have become about Japan's security.
And finally, for those with long memories, there is the question of whether Japan can be trusted to behave responsibly as a great power. Granted, Japan today is not the Japan of the 1930s and 1940s, and after 70 years it has earned the right to be trusted again.
But, at the same time, some people in Japan - including in the new government - find it hard to consider these urgent questions about Japan's strategic future without also revisiting questions about the past which should long ago have been put to rest.
For this reason many people in Asia will feel uncomfortable with the idea of Japan becoming a major power again. But we need to understand that unless Japan does this, the chances of a stable US-China relationship, and hence of a peaceful future for Asia, will be much diminished.
The writer is professor of strategic studies at the Australian National University's Strategic and Defence Studies Centre. He has been visiting Singapore as the S. Rajaratnam professor of Strategic Studies at the S. Rajaratnam School of International Studies.
By Invitation features expert views from opinion leaders in Singapore and the region.