By Geoff Miller, Australian Ambassador to Japan (1986-89) and Director-General of the Office of National Assessments (1989-95).

Recent reports from the Shangri-La Dialogue defence meeting in Singapore have put even more focus on the South China Sea and China's decision to put its new large drilling platform in an area that caused affront to Vietnam.

But while the exchanges at that meeting certainly sounded interesting, an even more interesting question is the one raised by Sam Roggeveen some weeks ago: given that this 'forward posture' is having such a harmful effect on regional and international reactions to China's rise, Sam asked, why is China doing it?

Clearly there are a lot of possible answers to this question. And at the outset we should note that for some years now Chinese commentators have reminded interested foreigners that there are now many voices and interests involved in the formulation of Chinese foreign policy. In regard to the South China Sea it is easy to discern two such interests: (1) the state-owned oil company CNOOC which, having built its drilling platform, wants to use it; and (2) the People's Liberation Army, with its interest in establishing China's strategic pre-eminence in its immediate region.

There may of course be more general motivating factors as well, and many of these have been canvassed on The Interpreter. They include a need on the part of the Party to boost its support and legitimacy by responding to nationalist sentiment, and possibly Xi Jinping's need to indulge the PLA in return for political support.

But senior figures in the Chinese Government must be only too aware of how China's aggressive stance in the South China Sea has raised Asia Pacific countries' fears, assisted Japan in its efforts to form an anti-China coalition in the region and helped the US justify its 'pivot to Asia', about which a number of countries initially had reservations. So to repeat, given these negative consequences, why is China doing it?

It seems to me that there are at least three big questions to which we should seek answers from the China experts. First, to what extent does 'the Chinese establishment' buy into the 'nine-dash line' theory of Chinese sovereignty in the South China Sea? If this is generally accepted and taken for granted we should not be surprised if China acts on it. If it is simply an ambit claim that people privately see as a try-on, it's a different matter (though that wouldn't exclude them trying it on).

Secondly, how intensely are resource pressures being felt or anticipated in China? Even though China has just concluded a major gas deal with Russia it is still dependent on energy imports from the Middle East, an area in the US sphere of strategic influence. Further, oil imports from the Middle East to China pass along extended sea lanes and through potential choke points — the Straits of Malacca in particular — which must make the thought of oil and/or gas from the South China Sea all the more attractive.

Thirdly, how concerned are Chinese policy-makers about the US, Japan and containment? We read and hear continually about China's increasingly aggressive posture and the need to react to it and take measures to counter it, but what are Chinese policy-makers reading and hearing about the American pivot and Japanese plans to mobilise South East Asian opinion against China? Michael Wesley spoke recently of a feeling of 'strategic loneliness' in Beijing, and Rory Medcalf has alluded to something similar.

It is certainly true that while some US commentaries speak positively about the future of US-China relations, others take a strikingly different tone. For example, in Foreign Affairs in 2012 Aaron Friedberg canvassed the option of blockading China, stopping its exports and preventing energy imports.

The rather ironic outcome may be that while the 'pivot to Asia' was greeted rather sceptically by some of America's Asia Pacific friends and allies, it may have caused all too much concern in Beijing, and with that concern a determination to strengthen its position as much as possible in strategic areas like access to energy supplies.

In stark terms, if China fears a possible US blockade, including of energy supplies, it could well decide to do whatever it takes to get access to energy supplies from an area close to it, to which it has or has manufactured a historic claim, and from which it would have shorter and less vulnerable lines of communication.

If this is the basis for what China is doing, it of course reveals a much harsher view of the possible course of US-China relations than those to which we are accustomed. And this is such a big issue that it is even more important than usual that we make every effort to understand the basis of 'the adversary's' position before entrenching ourselves in positions which may be based on an incomplete understanding of the factors driving it.

Photo by Flickr user BASF.