Sometime in 2012, or shortly thereafter, an American sergeant major in Seoul will haul down the flag of the four-star general who commands US forces in South Korea. It will then be transferred to Fort Shafter in Hawaii where that general or his replacement will assume command of all US Army forces in the Asia-Pacific region.

The shift of a top general will be among the final actions in a long, slow decline in the American engagement in Korea. Ten years ago, the US had 36,000 soldiers, sailors, airmen, and marines in South Korea. A year ago, that was down to 24,700, with many anti-American Koreans cheering and urging that more Yankees go home.

But conservative political leaders and many senior Korean military officers, retired and serving, deplored the cutbacks and pleaded with the US to maintain a larger contingent in Korea. The US agreed to level up those forces at 28,500 by 2012.

Moreover, the US will retain the mutual security with South Korea under which the US is obligated to help defend South Korea. As evidence of that commitment, the US has been lengthening the tours of troops posted in Korea and increasing the number of families accompanying those troops.

But senior US officers have told the South Koreans that they must be responsible for their own defense against communist North Korea and the departure of the top US general reflects that. Those officers have contended that South Korean forces are capable of deterring North Korea and, if deterrence fails, of repelling a North Korean attack, especially since Pyongyang's forces have been weakened by the rot in its economy.

Thus, in 2012, the US will turn over to South Korea the wartime command of its own forces. Today, South Korea has peacetime command of its troops but wartime control remains with the US, a vestige of the Korean War of 1950-53 that the US fought under the banner of the United Nations.

The mission of US forces in Korea is changing. Where their primary task has been to help defend South Korea, those US forces have become available to deploy elsewhere. They might rotate, for instance, to Afghanistan and return to Korea when that deployment was finished.

To prepare, the US is building a new post in Pyongtaek and modernizing its airbase at nearby Osan, both 85 miles south of the demilitarized zone that divides the peninsula. US forces will be consolidated, with about 26,000 of the 28,500 troops in Korea stationed in that complex.

From there, expeditions can be launched by air to wherever they are needed. What the US armed forces call "full spectrum training," meaning everything from counter-insurgency to nuclear war, has already started. In the event of hostilities, American families could be quickly rounded up and evacuated.

Moving the four-star general from Seoul to Honolulu is part of a realignment of US forces, including the command structure, in Asia and the Pacific. Having a four-star general in charge of US Army, Pacific, or USARPAC, will put that officer on an even footing with the four-star officers commanding Navy and Air Force components of the Pacific Command, which has its headquarters here.

In addition, Pacific Command will have a top Army officer to deal with other armies in Asia and the Pacific. More and more, the Pacific Command's mission is to forge partnerships with other military forces for joint training and operations. In most Asian nations, the Army is the predominant service.

In South Korea, a three-star lieutenant general will take command of US Forces Korea, the headquarters that controls Army, Navy, Marine, and Air Force units there. A similar headquarters in Yokota, west of Tokyo, controls US forces in Japan. Both will report to the Pacific Command in Hawaii.