Amid plans for a sweeping realignment of U.S. military services in Asia and the Pacific, the Army has begun extensive changes intended to turn it into the most flexible and expeditionary force it has been since the end of the war in Vietnam 30 years ago.

From Hawai'i, where the headquarters of the Army in the Pacific is situated, to the Pacific Northwest to Alaska, to South Korea and to Japan, the Army is being transformed, in the current buzzword of Secretary of Defense Donald Rumsfeld.

Says Lt. Gen. John M. Brown, commander of the Army in the Pacific: "Almost every one of our brigades and divisions, and all of our major headquarters, will be undergoing transformation over the next two years to better enable us to fight the war on terrorism or engage in any other military operation."

Last week, the Army activated a new air-defense command at Fort Shafter, headquarters of the Army in the Pacific. The 94th Air and Missile Defense Command can be deployed anywhere in the region to fight alongside the Pacific Air Force against aerial attack.

Next year, the first elements of a new Stryker brigade are scheduled to arrive at Schofield Barracks, the Army's main post in Hawai'i. The key equipment for the brigade's 3,900 soldiers will be 300 of the 20-ton armored vehicles that can be transported by air. Another Stryker brigade has been posted in Alaska, and three more will be formed at Fort Lewis, Wash.

Supporting the brigade combat teams for the first time will be a reconnaissance battalion equipped with long-range sensors, including unmanned aerial drones, and analysts to provide quick assessments to brigade commanders. Before, such capabilities were available only at higher levels, and it took time for intelligence to trickle down to combat commanders.

At Pearl Harbor is based an Army experimental ship, the twin-hulled catamaran Spearhead that can move Strykers, troops, and weapons at 40 knots for 2,500 miles. The Army plans to acquire 12 vessels, starting in 2010, with high-tech planning and communications gear that can prepare a force in transit to fight when it lands instead of needing time to get marching orders on the ground.

A brigade of paratroopers that was recently activated in Alaska has already shown an ability to overcome what U.S. military people call the "tyranny of distance" in the vast reaches of the Pacific. The brigade loaded 600 paratroopers into six C-17 planes, where they strapped on chutes in flight and flew 17 hours with aerial refueling to jump into northern Australia at one o'clock in the morning.

To set up a forward operational headquarters, the Army plans to move the I Corps headquarters from Fort Lewis to Camp Zama, a U.S. post southwest of Tokyo. Military officers said negotiations with Japan are progressing, and an agreement may be reached in time for President Bush and Prime Minister Junichiro Koizumi to announce it in November when the president visits Japan.

At the next level up, the Army headquarters in Hawai'i, known officially as United States Army, Pacific, or USARPAC, has been primarily responsible for providing trained and equipped troops to other commands in Asia and as far away as Iraq and Afghanistan.

"Over the next 18 to 24 months," Gen. Brown said, "things will change; we'll keep all our existing missions, but we will also become a war-fighting headquarters." That will require the command to devise war plans, prepare for contingencies and organize a staff to control forces across the full spectrum of military operations.

In addition, the headquarters of the Army in the Pacific is preparing to assume command of Army forces in South Korea, which are gradually being reduced and may eventually be largely withdrawn. Plans call for dismantling or shrinking the United Nations Command in Seoul that dates back to the Korean War that ended in 1953.

The Army also plans to transfer the Eighth Army headquarters from Seoul to Hawai'i and to turn back to the South Koreans control of their forces, commanded today by a joint U.S.-South Korea headquarters. The four-star American general's post in Seoul would move to Hawai'i.

Military officers say this could happen by 2008 or any time after. The official line is that the threat from North Korea must lessen and stability come to the peninsula first. The unofficial betting is that rising anti-Americanism in Seoul will cause that move to be made sooner rather than later.

Richard Halloran is a Honolulu-based journalist and former New York Times correspondent in Asia.