SEOUL -- U.S. Secretary of Defense Donald Rumsfeld is the man the world loves to hate. The blunt-speaking former wrestler has managed to infuriate U.S. friends and allies, declaring the nations of "Old Europe" irrelevant and undermining British Prime Minister Tony Blair on the eve of the Iraqi war by saying the United States could win without British troops.

Rumsfeld is a hard-nosed realist who makes no bones about the use of American military might. In the struggle for influence in Washington, his natural foil is Secretary of State Colin Powell, who favors diplomacy, coalition-building and the use of international institutions to exercise U.S. influence. In the aftermath of the victory in Iraq, on the heels of the rout in Afghanistan, the pendulum again has swung toward the Pentagon.

Rumsfeld's star is ascendant today, but on Sept. 10, 2001, he was public enemy No. 1 in Washington and there was open speculation about how long he would last in the job. Rumsfeld had bold plans to redesign the U.S. military, and his vision had alienated all the services and many of the important constituencies in Washington. Then on Sept. 11, a hijacked jetliner flew into the Pentagon and Rumsfeld led the rescue efforts. His heroism transformed the secretary's image and he has been going from success to success ever since.

Rumsfeld believes that the U.S. military is a big, lumbering beast, ill-suited to the demands of 21st century warfare and the technologies available to modern fighting forces. His vision of war-fighting envisions smaller, flexible units, capable of being deployed at a moment's notice wherever on the planet they might be needed. The contrast between that vision and the more traditional view of the service chiefs was evident in the runup to the attack on Iraq.

Rather than waiting for hundreds of thousands of troops to mass near Iraqi borders, as in the 1991 Persian Gulf War, Rumsfeld wanted to go with a much smaller force that could move quickly and outflank Iraqi resistance.

The strategy worked. In fact, its biggest problem was that the forces moved too fast, outrunning their supply lines and leaving rear units dangerously exposed. That experience validated Rumsfeld's earlier critique -- U.S. troops needed to be lighter and more mobile, not laden with the huge pieces of equipment that slowed down their movement and required huge logistic "tails" of their own.

The problem is that those huge pieces of equipment cost a lot of money to make. In other words, powerful vested interests -- in the Pentagon, on Capitol Hill and K Street (the center of Washington's lobbying industry) -- support their development and procurement. These vested interests were gunning for Rumsfeld before Sept. 11, 2001.

The balance for power has shifted in Washington since then. Not only has battlefield success favored the secretary of defense, but the recognition that 21st-century threats don't resemble those of the Cold War has strengthened his position. Conventional militaries aren't the best response to terrorist threats.

If there is a grand design for the U.S. military, it hasn't been revealed yet. Nonetheless, documents like the National Security Strategy, the Quadrennial Defense Review and the Nuclear Posture Review (officially classified, but portions have been leaked) provide valuable indications of administration thinking.

The key components of the new strategy are flexibility and mobility. Planners need to have more options and forces must be deployable as circumstances require. That has important implications for Asia.

First, there is less of a premium on bases and more of a need for "places" to preposition materiel and from which troops can be deployed. Second, forces have to be prepared for a wider range of contingencies, since they will be moving from place to place. This is especially important in South Korea, where U.S. forces have traditionally be tasked solely with fighting an invasion from the North. Military planners want those forces to be available for other regional deployments. Finally, the need for flexibility extends to doctrine as well: The administration has signaled its readiness to develop new nuclear weapons for particular situations.

There are some problems. First, the notion that nuclear weapons can be used for tactical reasons is very troubling. The administration believes that its current arsenal doesn't have deterrent value and new weapons are needed to restore its credibility. I'd argue that it is better to develop precision-guided munitions than erode the nuclear taboo.

The second problem is the perception that redeployment and reconfiguration raise questions about U.S. commitments. This has been especially evident in South Korea. Although many South Koreans have long wanted the U.S. military to reduce its footprint in the country, indications that the U.S. is ready to do just that raise fears that Washington will either abandon its ally or take its forces out of harm's way and then take some risky action -- like a preemptive strike against North Korea.

In addition to those long-standing concerns, there are fears that Washington would exact revenge on Seoul for the anti-Americanism that seemed to animate presidential candidate Roh Moo Hyun's campaign. Last week's summit between Presidents George W. Bush and Roh should put those fears to rest.

In the joint statement released at their meeting, the two men agreed to "a robust forward presence on the Peninsula" while promising to "consult closely" on military basing issues. That means consolidating U.S. forces, moving the Yongsan garrison at an early date and moving the U.S. bases that are north of the Han River. To quell South Korean concerns, the two men promised to "(take) careful account of the political, economic and security situation on the Peninsula and in Northeast Asia."

Concerns that the U.S. would abandon an ally are misplaced. A unilateral withdrawal would be fatal to regional confidence in the U.S. The notion that troops need to be in harm's way -- a "tripwire" -- is silly. There are thousands of U.S. citizens in South Korea and billions of dollars in U.S. investments. Troops aren't needed to guarantee the U.S. commitment to South Korean security.

As for revenge, Pentagon officials note that the two countries agreed over a decade ago to move Yongsan, a huge eye sore in the heart of Seoul. They also point out that the two governments agreed before last December's election to study U.S. deployments. U.S. thinking has been reinforced by the results of the Iraq war, but those are just "preliminary ideas."

Those ideas will be important no matter who is running the Pentagon. Political fortunes in Washington may shift, but the need to look hard at the U.S. military will not diminish. Security threats and challenges are changing in fundamental ways. Adapting to this new threat environment will not be pretty or easy. For all his faults, Rumsfeld is right to demand new thinking -- but expect more fireworks from the Pentagon as the process unfolds.