Much of the American and Japanese news coverage of the new security agreement between Washington and Tokyo has focused on its political aspects but overlooked the far-reaching strategic changes it has projected for the revitalized alliance.

This pact is intended to draw together a sweeping realignment of U.S. forces in Asia and the forthcoming revision of Japan's constitution. That revision is calculated to raise the Japanese military and diplomatic posture after six decades of pacifism that was the consequence of Japan's defeat in World War II.

Robert Scalapino, a prominent American scholar on Asia, noted the changes:

"Japan wants to be a major power," he said in an interview. "It wants to be in a partnership with the United States but not in a patron-client relationship."

The agreement on Oct. 29 was the most significant milestone in a process that began nearly three years ago when the Bush administration started negotiating with Japan to reposition forces, revise command lines, and make U.S. forces more flexible and responsive to contingencies.

Before the negotiations had gone far, the Japanese and the Americans agreed that they needed a basic reassessment of the alliance begun in 1952 after the postwar American occupation of Japan.

"We had reached a place in our alliance where we needed to look beyond force structures and to make fundamental changes in our roles and missions," said an American official aware of the negotiations who asked not to be named.

The outcome is the document titled "U.S.-Japan Alliance: Transformation and Realignment for the Future" signed by Secretary of State Condoleezza Rice and Secretary of Defense Donald Rumsfeld, and Foreign Minister Nobutaka Machimura and Minister of State for Defense Yoshinori Ohno.

In a news conference after the agreement was issued, Rumsfeld said: "Like all alliances, this relationship must and is in fact evolving to remain strong and relevant."

Ohno agreed, saying that the purpose of the earlier alliance was to defend Japan. Now, Japanese and U.S. forces could undertake joint operations elsewhere.

The agreement says: "These measures are designed to enhance the alliance's capability to meet new threats and diverse contingencies." Those "diverse contingencies," a term appearing repeatedly, were not specified but referred to potential threats from China, North Korea, terrorists and pirates in the shipping lanes of the South China Sea.

Key to Japan's deployment of forces alongside U.S. forces is the revision of Japan's constitution, especially Article IX, the "no-war" clause that has been interpreted as permitting Japan to defend itself but little more. A final draft is working its way through the ruling Liberal Democratic Party and the parliament.

The provision pertaining to national security says that in addition to operations to defend Japan, "defense forces can take part in efforts to maintain international peace and security under international cooperation, as well as to keep fundamental public order in our country."

The new agreement says the United States will continue to hold its "nuclear umbrella" over Japan: "U.S. strike capabilities and the nuclear deterrence provided by the U.S. remain an essential complement to Japan's defense," it says. That renewed guarantee should also blunt a Japanese move to acquire nuclear weapons, if it appears.

The agreement further says "a common operational picture shared between U.S. forces and the SDF (Japan's Self-Defense Force) will strengthen operational coordination."

That common assessment of potential adversaries will be reflected in joint training and jointly devised contingency plans.

The nuts and bolts of the U.S. force realignment, some of which were adopted to accommodate political demands in Japan, include establishing a joint operations center at Yokota Air Base, now a U.S. base, west of Tokyo. Japan's Air Defense Command will move from Fuchu, also west of Tokyo, to Yokota.

The U.S. Army will deploy a corps headquarters at Camp Zama, southwest of Tokyo, where Japan will set up a Central Readiness Force Command for its ground forces.

Bowing to political pressure on Okinawa, Japan's southernmost island, the U.S. Marines will move a headquarters and 7,000 marines to Guam, which is U.S. territory in the central Pacific. Some aircraft will be removed from a controversial base at Futenma and the airfield itself will be redesigned to move runaways away from residential areas. These changes in Japan's military posture have raised cries in China and the two Koreas that Japan is undertaking a full-scale rearmament. Cold-eyed scrutiny, however, shows that Japan's military spending is not scheduled to rise, its military forces are not slated to expand, and the defense industry remains small.

Honolulu-based writer Richard Halloran is a former New York Times reporter based in Asia.