Until recently, Japanese tanks had to wait at traffic lights in the event of foreign attack, a sign of sensitivities about military power in a country which renounced the right to wage war more than half a century ago.
By Sarah Buckley
BBC News Online
But growing concerns about North Korea and its missile capabilities, especially since it flew a ballistic missile over Japan in 1998, have forced Japan to face up to its defensive weaknesses.
As part of that process, the Japanese Government announced on Friday that it was buying a sophisticated anti-missile system from the United States.
Japan's purchase includes Patriot missiles, such as those used in Iraq
It comprises Standard Missile-3 (SM-3) systems capable of intercepting, from the sea, incoming ballistic missiles as they are in mid-course; and Patriot Advanced Capability-3 (PAC-3) systems capable of shooting down, from land, missiles about to hit the ground.
Friday's announcement was notable for the scope of its commitment - the programme is set to cost $7bn, and makes Japan only the second of the US' major allies, after Israel, to invest in a missile defence system.
But it is only the latest step in an ongoing collaboration on missile defence between Japan and the US, Tokyo's most important military and diplomatic ally.
Japan has already purchased four destroyers equipped with the highly-advanced Aegis radar system. It is these which will be fitted with the SM-3 missiles by 2011.
It is also taking part in research and development with the US to develop a new generation of the missile.
Robert Karniol, Asia-Pacific Editor of Jane's Defence Weekly, said that the missile defence project was being presented as a way to better protect Japan from potential attack from North Korea.
But it was also the result of heavy pressure from the US, which has 50,000 troops stationed in Japan and has been pushing its Asian allies to spend more on defence.
"It's very much a political thing. It has to do with the development of command and control communications that will better integrate the two military forces," he said.
The Japanese system could also be integrated into the US' wider ambitions for missile defence, though analysts are mixed on when and whether these will go ahead.
While North Korea represents Japan's most pressing worry, military planners who recommended buying the systems will have had other potential conflicts in mind.
"The public discussion you hear about the North Korean threat is just that. It's for public consumption. (The system) is as much geared to China... but they don't like to talk about that," Mr Karniol said.
Many analysts believe China's growing economic power will lead to a more confrontational stance towards Japan, its only potential Asian rival.
It is much easier for Tokyo to highlight the present threat from North Korea, with which it has very poor relations, than risk domestic and international alarm by mentioning any future threat from China.
But there are concerns that however much Japan spends on missile defence, the systems could provoke exactly the belligerence they are designed to thwart.
If North Korea, and maybe even China, believe their offensive capabilities are no longer good enough, they may decide to spend more money on improving them.