As 2003 ends, Japan is embarking on some far-reaching changes in its defense policy that will give it greater strategic flexibility and make it a stronger ally of the United States. The big question is how China and the rest of Asia will react.

Earlier this month, Tokyo finally decided to send its first air force unit to Iraq to prepare for the arrival of Japanese ground troops, after a lengthy delay because of safety concerns and public apprehension in Japan.

Despite such worries, the government of Prime Minister Junichiro Koizumi is pressing ahead, arguing that the mission to Iraq is important to sustain the U.S.-Japan alliance for any future crisis in Asia.

North Korea's nuclear and ballistic missile ambitions, and terrorism, are at the forefront of official concern in Tokyo about the new threats facing Japan. The controversial commitment to help out in Iraq is a goodwill down payment that seeks to ensure future U.S. support if Japan is attacked or threatened by North Korea.

Of course, Japanese troops in Iraq will be engaged in humanitarian and reconstruction efforts, and armed only for self-defense. But it is, nonetheless, the first Japanese military deployment since World War II in a country where fighting is still going on and where a peacekeeping operation sanctioned by the United Nations is not involved.

Critics assert that this conflicts with Japan's postwar pacifist Constitution, which bans the use of force in settling international disputes and permits the country to maintain military forces only for the defense of Japan.

Just as significant as the Iraq deployment is Japan's decision this month to join the United States in putting in place a missile defense network in the Asia-Pacific region to guard against attacks from North Korea. Australia, another long-time ally of America, had earlier announced that it, too, would participate in the program.

It is being developed by the United States to provide protection for itself and its allies against emerging threats from so-called "rogue" nations, or even terrorist groups, with ballistic missiles that could one day be armed with nuclear, chemical or biological weapons.

The decision of Australia and Japan indicates that neither nation expects North Korea to agree any time soon to get rid of its weapons of mass destruction and the means to deliver them. Their decision also poses a new test of China's strategic interests and policy in Asia.

The Japanese government said Dec. 19 that it would buy from the United States a two-stage defense system to shield Tokyo and perhaps other major cites from attack by North Korean missiles. The Japanese Defense Agency expects to spend at least $4.2 billion to bring the system into initial operation by 2007 and full deployment by 2011. This does not include maintenance and operating costs. They might bring the total bill to well over $8 billion.

The shield Japan will acquire is designed to detect a hostile missile as soon as it is launched. Japan will use SM-3 missiles on its four destroyers equipped with the Aegis advanced electronic tracking and command and control system to intercept an incoming missile in its mid-course phase beyond the Earth's atmosphere.

If that first-stage defense fails, a different missile, the Patriot Advanced Capability-3, known as PAC-3, will be launched from the ground in Japan to shoot down an incoming missile in the terminal stage of its flight. The PAC-3 interceptor has a mixed record of success.

The United States praised Tokyo's decision to buy into the controversial missile shield program. Critics say the technology for such shields - dubbed Son of Star Wars - is complex, unreliable and expensive, and that the plans could spark a new arms race.

But Japan says that the technology is maturing, while Australia's Defense Minister Robert Hill makes the point that with nuclear proliferation already occurring among states that do not follow international rules, there is no better alternative than the U.S.-led program.

Japan has been taking part in joint research with the United States on missile defense since North Korea test-fired one of its long-range missiles over northern Japan in 1998. Japan currently has no way of protecting itself from a ballistic missile attack.

Until Japan's shield is in place, the United States is considering using its own Aegis warships armed with SM-3 missiles to protect Japan and U.S. forces stationed there from a North Korean ballistic missile attack. The United States is in the midst of testing its sea-based Aegis and SM-3 anti-missile program and will not finish until 2005.

Japan's move to acquire a missile shield is particularly significant and is premised on a major shift in its defense policy. During and even after the Cold War, the main threat was perceived to come from a large-scale invasion of the Japanese home islands by the Soviet Union or China.

Now the chief threat is seen to be terrorism and missile strikes, most immediately from North Korea.

This was set out for the first time in August in Japan's 2003 White Paper on Defense. It noted that the spread of weapons of mass destruction and ballistic missiles in the hands of dictators, and perhaps in future of terrorists as well, had completely changed existing concepts of war and defense. The White Paper said that Japan must be able to respond, quickly and effectively, to these new types of threats.

"The danger and possibility of a land invasion have become extremely low," said Japanese Defense Agency director-general Shigeru Ishiba.

When Mr. Ishiba visited China not long after the White Paper was published, the Chinese Defense Minister Cao Gangchuan cautioned that if Japan were to get a missile defense system it might "promote an arms race" in Asia.

China has long argued that even a purely defensive missile shield could challenge the deterrent value of its nuclear-armed ballistic missiles, making it necessary to expand and modernize the arsenal to keep it effective.

Indonesia, too, has expressed concern that a missile shield in Asia and the Pacific will create uncertainty and instability. "First of all, we would like some transparency, we would like to know exactly to what threat it is directed," Indonesian foreign ministry spokesman Marty Natelgawa said after Australia announced that it was joining the U.S. program.

The Australian government, which has briefed China and other Asian nations on the reasons for its decision to help the United States in developing the missile umbrella, has promised a written explanation to Indonesia, at Jakarta's request.

Ironically, however, it is virtually certain that Japan will have to undertake substantial cuts in its army firepower to pay for the missile shield. The White Paper said that because the threat of a large-scale invasion of Japan in the near future was low, the government would consider reductions in weaponry needed to repel such an invasion on land, including tanks and artillery.

To collaborate with the United States on missile defense, Japan will have to lift, at least partially, its ban on arms exports so that it can sell to America components or parts related to the program. The ban has been in place since 1976 and was seen by Japan's neighbors in Asia as a significant assurance of nonaggression.

Japan may also have to change its war-renouncing Constitution, which allows self-defense but not collective defense. The Koizumi government argues that the missile shield does not violate Japan's self-imposed ban on collective defense, which the United States argues is outmoded and undermines the bilateral alliance.

Critics say that under current provisions in Japan's Constitution, the launch of a missile defense interceptor from Japan against, say, North Korean long-range ballistic missiles aimed at the United States or any other third country would be regarded as collective defense and therefore illegal. Japanese officials insist that they will be able to distinguish incoming missiles targeted at Japan from others. However, this is a moot point.

A North Korean Nodong missile, which travels at a speed of up to 4 kilometers per second, would take only about 10 minutes to hit Japan after launch. So the Japanese government will probably need to change the self-defense law. It requires the prime minister to get approval from the Security Council and Cabinet before issuing a defense mobilization order that would allow the military to activate the missile defense system.

A shortened procedure is clearly needed. It has been calculated that following existing rules would take approximately 30 minutes. This is far too slow to prevent an incoming missile strike.

The writer, a former Asia editor of the International Herald Tribune, is a visiting senior research fellow at the Institute of Southeast Asian Studies in Singapore. This is a personal comment. - Ed.

By Michael Richardson The Straits Times / Asia News Network