The world and Japan have lived comfortably for a half-century with the illusion that Tokyo could permanently renounce its strategic ambitions beyond promoting economic gain for its companies and citizens. This illusion is dissolving, step by agonizingly slow step.

The movement is almost imperceptible. But it goes in one constant direction: toward greater self-reliance in military and security affairs and international politics. The essential bargain of the Cold War era in which the United States seemed to handle these matters for a politically passive Japan is gradually unraveling.

This rainy Tokyo spring has been a critical moment in this evolution. The war in Kosovo, America's multiple problems with China, growing uncertainty over North Korea's intentions and economic depression at home have jolted Japanese policymakers out of any feeling of complacency with the status quo.

Japan has responded outwardly to each of these developments by stressing continuity in the policies it has followed since its disastrous defeat in World War II.

Japan is providing limited rhetorical and financial support for America's air war on Serbia. It tries to keep the two impulsive giants with which it must live, China and the United States, from going to extremes in their relationship. On North Korea, it carefully calibrates the amount of aid needed to keep the Pyongyang regime afloat against the amount of confrontational language and action needed to keep it in line.

These predictable responses reflect Japan's continuing need for a strong security alliance with the United States, and the fact that Japan's public and politicians are generally comfortable with the restrictions the country's antiwar constitution imposes on its international role.

But subtle signs of change in outlook and the laying of a foundation for greater activism in world politics in the future were also apparent on a recent visit to Tokyo.

One was a low-key but symbolically important Japanese decision to design, build and launch within four years four wholly Japanese reconnaissance satellites, despite U.S. entreaties to buy cheaper, more powerful American satellites. One official told me Japan would also resist expected U.S. pressure for a joint satellite project, adding: "This is technology we will develop on our own."

North Korea's firing of a new test missile into the Sea of Japan last August is cited as the trigger for the satellite effort by several officials. "There is a need here to cover North Korea on a more regular basis than U.S. satellites can, given their global responsibilities," said one.

The fallout of a series of hostile North Korean actions, including the sending of spy vessels into Japanese waters this spring, has been broad and deep. "This has created tensions and increased our awareness of the needs of self-defense," says Munio Suzuki, a leader in the ruling Liberal Democratic Party who holds the influential post of deputy cabinet secretary in Prime Minister Keizo Obuchi's government.

Japanese officials have been uncomfortable with South Korean President Kim Dae Jung's seemingly unquestioning pursuit of better relations with Pyongyang's erratic, famine-ridden regime and Washington's support for Kim's "sunshine policy." The number one nightmare in Tokyo is a suddenly unified Korea with access to nuclear weapons.

"As long as the United States, Japan and South Korea retain firm ties and close cooperation, there will be no cause for concern," Prime Minister Obuchi told me in a curiously conditional formulation. A lower-ranking official speaking on background put Japan's concern more directly: "Will the United States keep a unified Korea non-nuclear? The answer to that will determine whether we have to think of going nuclear ourselves."

America's wildly volatile relationship with China also perturbs the strategic picture in Northeast Asia. Some Japanese officials feel President Clinton should have sent Secretary of State Madeleine Albright to Beijing to apologize in person for the bombing of the Chinese Embassy in Belgrade as, they suggest, Beijing requested. Others voice concern that Washington does not seem to have grasped how seriously the bombing, the festering dispute over Chinese membership in the World Trade Organization and other conflicts have undermined the current Chinese leadership.

Obuchi will travel to China in July with a new set of made-in-Japan priorities and objectives that have been taking shape in recent months. They will not conflict with those of the United States -- nor will they any longer automatically be exactly the same. A subtle process of change that Washington needs to watch more closely has seen to that.