Hatoyama fought back tears announcing his resignation, but few people will shed any for him. He failed to show leadership, or even basic political intelligence, not only over the decision not to move the US Futenma base but on a wide range of issues. The Japanese people recognised this, giving him a popularity rating of 74 per cent after the sweeping election victory last August and only 17 per cent by last weekend.

Indeed, his resignation speech was Hatoyama's finest hour. He managed to ensnare 'Shadow Shogun' Ichiro Ozawa in his resignation embrace, with Ozawa promising to step down as secretary general of the Democratic Party of Japan (DPJ) along with his backroom henchmen. If Ozawa also relinquishes the role of kingmaker, it is potentially a huge advance that will free the new prime minister.

Hatoyama gave Ozawa more than a shove towards the exit when he said: 'I told him 'I'll resign, and I want you to resign, too. This will enable the party to create a new DPJ and a clean DPJ'. He agreed, saying, 'I understand'.' Ozawa, however, is someone who, in the classic parlance, knows where the bodies are buried. He chose most of the DPJ members of parliament in last year's election and may be reluctant to surrender real power.

Hatoyama's other parting shot was his dream that, as he put it after announcing his resignation: 'Someday, the time will come when Japan's peace will have to be ensured by the Japanese people themselves.' This shows the dangerous mixture of dream and illusion that tempts Japanese politicians who feel their masculinity and Japan's independence are threatened by reliance on the shelter of the US nuclear umbrella.

Surely the supreme irony is that Hatoyama broke his promise about moving the Futenma base completely off Okinawa, signed the deal with Washington, then resigned citing the broken promise as his reason, but leaving his successor to deal with the details and the repercussions of implementing the deal.

Washington has shown its shallow understanding of what is at stake by repeating that the Futenma base deal is between the two governments, not between particular politicians, and parroting that the US-Japan security agreement is the keystone of the two countries' strong and stable relationship. In other words to Japan: it's your problem, not ours.

But Washington's and Tokyo's problem is that even the revised deal that Hatoyama reaffirmed over the relocation of Futenma may not be possible to implement, not least because the opposition within Okinawa is too strong. It is no longer a question of a handful of opponents who will be directly affected, but has become something of a crusade among tens of thousands of Okinawans that the islands have suffered too much from war and that they don't want any more American troops.

Japanese realists know that, in the modern world, few countries can rely entirely on their own defences. Singapore's founding father Lee Kuan Yew pointed out recently that Japan is just too small to be a counterweight on its own to the burgeoning political, economic and military might of its giant neighbour China.

China has recently shown its muscles to Japan even as links between the two countries are growing rapidly. When Chinese naval vessels were exercising in international waters close to Japan in April, Japanese vessels went to check and got buzzed by a Chinese military helicopter. China's ambassador in Tokyo blamed Japan for un-neighbourly conduct in checking on the Chinese fleet.

Economic ties with China are becoming too strong; it is inconceivable that any DPJ government will change course. There is too much Japanese trade and investment in China at stake and potentially too much Chinese tourist income for Japan.

If Obama insists - as his spokespeople have - that Japan must implement the Futenma deal in the face of rising opposition and demonstrations in Okinawa, Tokyo may back away and the whole US-Japan partnership could be at risk. Better to show statesmanship in advance: offer some consolidation of US bases and co-operation between American air, navy and marine forces and respect for the burden on Okinawa. Who knows, if Washington tried, it might work out a better deal both for itself and Japan instead of having another volcano blow in Obama's face.

Kevin Rafferty is author of Inside Japan's Powerhouses, a study of Japan Inc and internationalisation