LATE in August Prime Minister Yasuhiro Nakasone stood in the Japanese parliament and declared that, in theory, Japan could send minesweepers to the Gulf. It was the first time since World War II that a Japanese leader publicly raised the possibility of sending armed forces abroad.
Privately, says a source close to him, Mr. Nakasone was seriously contemplating dispatching the ships. The boldness of the step appealed to him. It would be a show of Japan's new willingness to exercise a responsibility in world affairs commensurate with its status as the world's second-largest economic power.
Many of Nakasone's advisers balked at the idea. Ultimately, he considered the political storm such a move would probably generate and settled for nonmilitary measures to assist Western security efforts in the Gulf.
The Gulf policy illustrates two fundamental and apparently contradictory aspects of security policy during the Nakasone era. The prime minister has displayed the courage and the desire to break many of the postwar taboos surrounding defense. At the same time, when it came to concrete actions he has ventured carefully, within the bounds of consensus.
This duality accounts for the two different assessments of Nakasone's security policy that emerged in talks with Japanese defense experts. Many give Nakasone little credit for whatever happened during his nearly five-year rule - the basic policies were already decided, they say. Nakasone merely presided over a gradually evolving Japanese security role.
Others contend that Nakasone has made a great difference, that without him the Japanese government would have been unable and unwilling to make certain tough decisions. This is often expressed by his critics on the left who see him as the agent of Japanese militarization.
Nakasone's greatest asset is his interest in defense issues. A former Imperial Navy officer, Nakasone is the only premier to have served previously as the defense minister, in the early 1970s.
Koichi Kato, the director general of the Japan Defense Agency under Nakasone, recalls sitting in the parliament, watching Nakasone handle questions on defense. ``I felt that Nakasone had studied defense policy issues very closely, very intensely. Whereas when it came to domestic, especially economic affairs, we could sense that he did not like the issues too much.''
This deep personal interest has been interpreted by many Japanese critics as evidence of his hawkish, nationalist ideology. Among American observers, Nakasone has been characterized as a Gaullist, one who would pursue an independent military buildup. What has surprised many is the extent to which he has pursued a thoroughly internationalist agenda.
There is general agreement about what were the most significant changes in security policy during this period:
The decision to abandon the ceiling on defense spending which had limited it to under 1 percent of Japan's gross national product (GNP).
The agreement to cooperate on defense technology with the US, including the decision to join the ``star wars'' antimissile defense research program.
The expansion of military cooperation with US forces, emphasizing the joint defense of western Pacific sea lanes.
The active role Japan has begun to play for the first time in Western nuclear strategy, including disarmament negotiations, particularly in the area of intermediate nuclear forces (INF).
IN 1976, the Japanese government adopted the National Defense Program Outline, a comprehensive statement on defense policy. The program specified force and equipment goals for the military, defined the role of those forces, and set a ceiling for spending of 1 percent of GNP.
While it had no legal status, the spending limit acquired an almost constitutional stature. It was an important symbol of containing Japan's buildup to a purely self-defense capability.
For Americans, the GNP cap became a sore point, lending credence to the charge that Japan was having a ``free ride'' on defense. American defense spending amounts to about 6 percent of GNP and Western European nations' from 3 to 6 percent.
Japanese defense spending rose steadily during this period, averaging a growth rate of more than 7 percent per year. During the Nakasone years, as spending grew and economic growth slowed, the ratio pressed up within hundredths of a percent of the limit.
Nakasone stated his desire to change the policy, hoping at least to remove an irritant in US-Japan relations and to free defense spending from that artificial barrier. More than once he hesitated in the face of resistance from within the ruling party and the bureaucracy.
Nakasone gets personal credit from all sides for the decision, finally taken last year, to officially end the limit.
``If the prime minister were not Mr. Nakasone, then the 1 percent ceiling would not have been abolished,'' says Mr. Kato.
Defense needs, Kato says, could still have been met if spending remained within 1 percent of GNP. As it was, spending went up marginally to 1.004 percent.
In the view of Kato, the most important contribution Nakasone made was ``that the Japanese government, for the first time under Nakasone's leadership, committed to go along with the United States on the development of military technologies.''
The most controversial result was Japan's decision to join the Strategic Defense Initiative (SDI) research program. To do that, Nakasone had to cross another symbolic barrier - the postwar ban on the export of military technology and hardware. The export ban has two aims - to block even a hint of an overseas military role and to restrain the growth of the defense industry.
Since the late 1970s, Japanese industry, with funding from the Defense Agency, has been producing sophisticated weapons, such as missiles, based on breakthroughs in civilian technology. In response, the US Department of Defense has wanted to end the one-way flow of technology to Japan in favor of two-way cooperation.
An agreement to exempt the US from the ban on the export of defense technology was drawn up before Nakasone became prime minister, under former Prime Minister Zenko Suzuki. But the Cabinet and premier balked at making the pact final.
The decision to go ahead came early in the Nakasone administration, in November 1983.
The most important consequence was that the agreements became the framework for Japanese companies to contribute their technology to the star-wars research effort.
NAKASONE personally supported the Reagan administration invitation to join the SDI program. But it took two years before the bureaucracy, with the backing of the ruling party, could complete its ``study'' and give the go-ahead. A Western diplomat argues, if there had been another man in the office, ``we might have ended up with a less-supportive political policy.''
As a result, Japan joined only four other Western allies (Britain, West Germany, Italy, and Israel) in signing a government-to-government agreement under which private companies can join research projects.
Even though Japan is bound to the United States by a Mutual Security Treaty, the extent of actual cooperation between the two militaries has been very limited.
Under Japan's US-imposed ``peace Constitution,'' its armed forces can only be used for the defense of the nation's territory against attack. The Constitution bars participation in any form of collective defense pact, such as NATO.
In recent years, the Japanese government has slowly stretched the limits of self-defense. During the Nakasone administration, US and Japanese forces have engaged in extensive joint training maneuvers, along with detailed contingency planning for deploying troops together in a crisis. Japan has been acquiring more sophisticated air and naval weapons, designed to counter the Soviet buildup in the Far East.
None of this is the result of Nakasone's efforts, however. The basis for this was laid in the mid-70s, when discussions began that led to a 1978 US-Japan agreement on defense cooperation.
The most striking innovation was made by Prime Minister Suzuki, during a visit to Washington early in the Reagan administration, when he committed Japan to defense of the sea lanes up to 1,000 miles from Japan's shores. The sea-lane defense concept, says the Western diplomat, was ``as revolutionary a departure as anything Nakasone has done.''
Motoo Shiina, a ruling-party member of parliament, considered the party's leading voice on defense affairs, summarily views Nakasone's security policy as ``an extension of the policies declared at the Suzuki-Reagan summit.''
But Nakasone certainly contributed by speaking more forthrightly on these issues, helping to increase public acceptance of the need for a stronger military.
Nakasone, the diplomat concludes, ``is someone known to be favorable to expanding defense cooperation.''
``It gives those in the bureaucracy more confidence to have someone at the top articulating these things,'' he says.
If Nakasone did anything truly unprecedented, it was his participation in the discussion of global security issues at the summit meetings of Western leaders.
Nakasone made a distinct mark at the first summit he attended, in Williamsburg, Va., in 1983. President Reagan was seeking Western European agreement on a strategy of carrying out deployment of US intermediate-range nuclear missiles in Western Europe, while pursuing a negotiating strategy with the Soviets calling for complete elimination of those weapons.
BY many accounts, Nakasone surprisingly stepped in to play a crucial role in that summit's mediations, which concluded with an allied Western security policy on INF.
``If anyone else had been in his position,'' Mr. Shiina says, ``he wouldn't have done that. He would have kept silent while the other heads of state were talking about strategy.''
Nuclear strategy has been one of the strongest of the postwar taboos, reflecting the passionate antinuclear feelings of the only nation to have been atom-bombed.
``Before that,'' observes former Defense Minister Kato admiringly, ``the Japanese prime minister tended to think that since we had no global weaponry systems - [because] we don't have nuclear capacity and we don't have any offensive weaponry - we are not qualified to participate in global disarmament issues.''
Nakasone's leadership skills are undeniable, and they have brought tangible changes in the way Japan conceives of its role in the global security system. But he has articulated a policy path that was laid before his advent to power, and which will continue beyond his tenure.