All of which makes him very different to the last two holders of the defence portfolio.

Described by some as a 'cold theorist', Morimoto was raised with three siblings by a single mother and reportedly relies on shots of vinegar drinks at the end of a tough working day to relieve fatigue and stress.

He is likely to require a good stock of vinegar in his desk at the ministry in the months ahead.

The announcement on Monday by Prime Minister Yoshihiko Noda of the appointment of 71-year-old Morimoto as defence minister took many people by surprise.

That a new defence minister was named was much less of a surprise.

Yasuo Ichikawa and, most recently, Naoki Tanaka, did little to enhance their political reputations in office, both showing little understanding of - or interest in - defence issues.

Tanaka was censured by the opposition Liberal Democratic Party (LDP) in the upper house of parliament in April for his ministry's poor handling of Japan's response to North Korea launching a rocket.

Aside from Tanaka's failures, the prime minister needs to win the support of the opposition to push through tax reform bills, in part to pay for the reconstruction of parts of northeastern Japan devastated by last year's earthquake and tsunami.

Morimoto is arguably the ideal defence minister for the opposition, although the LDP put up a token protest by suggesting it was inappropriate for an unelected citizen to hold a ministerial post.

'The LDP has made a lot of noise, but that's just politics,' said Jun Okumura, a senior adviser and political analyst with the Eurasia Group.

'I would say that Morimoto's thinking is very much in line with the mainstream attitudes of the defence establishment here, and I think that is apparent from his extensive writing and interviews on security issues.

'He is not interested in provoking China, unlike [Tokyo] Governor Shintaro Ishihara.

'But he is definitely on the conservative side and in tune with those elements in both the LDP and the ruling Democratic Party of Japan.'

Ishihara said in April he planned to buy three of the uninhabited Diaoyu Islands - known as the Senkaku Islands in Japan - from a private Japanese investor, and vowed to protect them, without specifying what that would involve.

The announcement sparked protests from Beijing. The islands are a recurring flashpoint between the two countries, underlined by a 2010 collision between a Chinese fishing vessel and Japanese coastguard ships nearby that frayed ties for months.

Only last week, Japan's envoy to China, Uichiro Niwa, told London's Financial Times newspaper that Ishihara's plan to buy the islands in the East China Sea could cause 'an extremely grave crisis'.

The comments led to him being cautioned by the government.

Unusually, Morimoto was first employed by the LDP before it was ousted from power in 2009.

He served as an adviser to the government on the realignment of US forces in Japan and other security issues.

For the last two months of the administration, he served as an aide to the defence minister.

Morimoto has dedicated his working life to military issues.

A graduate of the National Defence University, he served for 14 years in the Air Self-Defence Force and was director of national security policy at the Foreign Ministry.

He has balanced the bureaucracy with punditry on security policy and every year is estimated to give around 150 lectures and make more than 100 television and radio appearances to discuss topics ranging from conflicts in the Middle East to the potential threat emanating from Beijing.

Throughout his career, Morimoto has expressed the belief that Japan should do away with the provision that it cannot take part in 'collective defence'. It means Japanese troops are not permitted to assist allied or friendly states unless Japan is itself directly attacked.

A legacy of the second world war, this has long been considered one of the key issues that sets Japan aside from other nations.

Now it is widely believed that the nation should take steps to turn itself into a 'normal' nation state.

Given the number of years that have passed since the end of the conflict, the sense is that it would be the natural thing to do.

It is too early for Morimoto to have indicated his intentions in that area, but there are two other key issues he has had to face up to from his first day in office. One is the matter of US forces on Okinawa and the relocation of the functions of the US Marine Corps' Futenma Air Station.

The second is China.

The people and politicians of Okinawa reacted with something approaching disdain when Morimoto's name was announced,.

That's because he is a convinced advocate of the existing plan to shift the marines from Futenma to an enlarged facility at the existing Camp Schwab, on the northeast coast of the prefecture. The people of Okinawa want the marines to depart more permanently, either to Guam or mainland Japan, which they believe is failing to share the burden of US forces equally.

And while the question of how that matter plays out will be of interest in Beijing, more importance will be placed on Morimoto's view of China in the evolving Asia-Pacific paradigm.

Morimoto was interviewed by the Sunday Morning Post in November 2010, when he was a professor of world studies at Tokyo's Takushoku University.

He said he believed the strategic defence review, due to be released the following month, would lead to a lifting of the ban on military exports - a prediction that is in the process of coming true - and that Japan could station troops on the Senkaku Islands.

That has not, as yet, happened, Ishihara has been forcing the issue with his plans to buy some of the islands from their private owners.

'I believe the outline will mark a turning point in our strategic and defence planning,' Morimoto said of the review, which shifted the country's defence focus from the Soviet cold war threat to its southern islands near China.

'There is a strong sense now that Japan has to react to an aggressive change in China's foreign policies.

'What is Japan's leverage to deal with China?' he asked. 'That is what we are talking about now. As China grows and becomes stronger, we can see that the main leverage we will have left is military.'

Japan spends around 1 per cent of its GDP on its military.

But while the armed forces are relatively small, it employs some of the most technologically advanced battlefield systems in the world.

'The Japanese people are scared of China now,' Morimoto said. 'But it is unlikely that they will want to spend much more on defence.'