The phased pullback of more than 14,000 American troops far from the demilitarised zone separating North and South Korea is the latest step in a sweeping global rearrangement of US military forces, conceived in the aftermath of the Cold War, and hastened by the war against Saddam Hussein.
The withdrawal from what is frequently described as the "most dangerous place in the world" would take years, senior Pentagon officials said, and, for the time being at least, would not affect overall US force strength in South Korea.
Its immediate aim is to prevent Washington from automatically being dragged into a conflict between the two Koreas. As Paul Wolfowitz, the deputy defence secretary, put it this week during a visit to Seoul: "This is a time to move beyond outmoded concepts or catchphrases such as the term 'tripwire'."
The redeployment, long resisted by a nervous Seoul, reflects the new emphasis by the Pentagon of Donald Rumsfeld, the Defence Secretary, and Mr Wolfowitz, on a nimbler, more hi-tech US military, less reliant on the costly permanent deployment of 200,000 or more troops and their families in foreign countries that often resent their presence.
The new focus will be on swift-striking "expeditionary" forces, based as far away as the United States, to be dispatched to trouble-spots. These will be able to draw on equipment stored at "skeleton bases" around the world. Iraq offered a foretaste of what is to come, because some of the tanks and supplies used for the invasion had long been stockpiled in bases in Kuwait and elsewhere.
Of the global redeployments, the most dramatic will be in Europe and Saudi Arabia. The present US garrison of 80,000 men in Germany reflects a threat that vanished more than a decade ago, a thrust by Soviet and Warsaw Pact forces through the Fulda Gap into old West Germany. Now the 16,500 men of the US Army's 1st Armoured Division will not be returning to their previous bases in Germany when their mission to Iraq is completed. They will either go back to the mainland US, or to new bases in eastern Europe. Poland, Bulgaria and Romania are among the possible destinations. The future of even the giant air base at Ramstein, near Frankfurt, is not certain.
This particular shift in America's military "footprint" follows the new political and diplomatic realities brought about by the war to topple Saddam Hussein. Germany, which opposed the conflict, is no longer in Washington's good books. By contrast, the former Soviet countries most certainly are, foremost among them Poland, which wants to assume substantial peace-keeping duties in Iraq.
They have the additional advantages of being far cheaper, less populated and with fewer restrictions on permitted activities. The largest available training area in Germany is only 18,000 acres, compared with 400,000 acres at the Pentagon's National Training Centre in California alone.
An even more important change is happening around Iraq. The US pullout from Saudi Arabia will remove a grievance that has fuelled the cause of Osama bin Laden as he calls on Muslims to drive the "infidels" from the country that guards Islam's holiest places. Instead America is setting up new, probably permanent, bases in what it intends to be a friendly, secular and democratic Iraq next door.
Its regional command headquarters has already been moved from Saudi Arabia to Qatar. The shifts have the extra advantage of bringing US strike-power closer to the borders of Iran, to discourage Tehran from meddling in Iraq and from pursuing its suspected nuclear weapons programme.
Now that the need to keep Saddam Hussein "in his box" has disappeared, Washington is also scaling back its presence at the Incirlik air base in southeastern Turkey.
Economic and military factors have weighed, as well as the desire, many suspect, to punish Turkey for its refusal to sanction the launch of a northern front against Baghdad.
So America is quietly strengthening its foothold in countries such as Uzbekistan and Kyrgystan, closer to Afghanistan, a likely flashpoint on the great "arc of instability" across the Arab and Islamic world that will last many years. It may later scale back its presence of more than 40,000 troops in Japan.
The changes in the field are being accompanied by a personnel shake-up at the Pentagon. Mr Rumsfeld has taken particular aim at the US army, the service he regards as especially wedded to what the former Soviet president Mikhail Gorbachev used to call "the old thinking".