Bring home US troops? Hard to do.

As a candidate, George W. Bush criticized what he termed "overdeployment" of US troops abroad. As president, he confronts this reality: Bringing Americans in uniform home is a lot more difficult than it looks.

In part, that's because today's regional geopolitical fires are difficult to extinguish. Just look at the Balkans, where US operations are now expanding into yet another troubled country - Macedonia - under Mr. Bush's watch.

But it's also due to the fact that many of the military's most grinding, large-scale operations serve the nation's basic security commitments. It's possible to scale back Air Force enforcement of the no-fly zones over Iraq, of course, or repatriate thousands of Army troops from the Korean Peninsula. It's just that doing so would likely mark changes in the US position in the world, beyond even those imagined in the new administration's many defense-policy reviews.

"The vast majority of American military personnel deployed abroad are not participating in peacekeeping operations in the Balkans or anywhere else," writes Brookings analyst Michael O'Hanlon in the journal Foreign Affairs. "They are protecting the United States' core interests and allies on long-standing and eminently sensible missions."

As top generals and admirals remind Congress in virtually all of their committee appearances, the US military today remains a far-flung force. On any given day, approximately 121,000 Army soldiers, 87,000 Air Force airmen, and 99,000 Navy and Marine personnel are on permanent or temporary duty overseas, according to the service chiefs. That's about 20 percent of the military force.

Joining up remains a way for young Americans to see the world. Typical servicemen or women can expect to spend about 20 percent of their careers outside of the United States. Some try to make it more: The Navy has a certain portion of sailors who try to spend virtually all their time afloat. The service thus may have a hard time meeting congressionally mandated goals to reduce deployment "personnel tempo," Adm. William Fallon, vice chief of naval operations, told a House panel in June.

The military is doing at least a little in lots of places. The Army alone has a significant presence in at least 100 countries. But the bulk of US troops abroad remains concentrated in a few areas where allied relationships or ongoing operations have been judged crucial to national security by a succession of commanders-in-chief.

The military's balance between long-standing commitment and short-term peacekeeping is perhaps clearest in Europe. The Soviet Union is receding in memory, but America's permanently stationed forces in Europe still number about 100,000 troops, down from 300,000 at the height of the cold war.

Reportedly, Defense Secretary Donald Rumsfeld has considered withdrawing portions of this force as a way to save money. Some analysts outside government say this is a good idea.

With the European Union now developing its own defense forces, the US could reduce its presence on the continent by three-quarters without damaging its interests, according to Lawrence Korb at the Council on Foreign Relations. That's not what the military thinks. Given peacekeeping demands, support for forces operating in the Persian Gulf, and continued NATO requirements, current numbers "must be considered the minimum level needed," Air Force Gen. Joseph Ralston, US European Command commander-in-chief, told Congress recently.

The hottest spot in Europe remains the Balkans. The expansion of US operations in Macedonia will not mean an increase in the number of US personnel in the region, Mr. Rumsfeld insisted this week. That mission is being carried out by US forces already in Kosovo. And the number of US troops in the area is far below its late-1990s peak, mostly due to a drop in the Bosnia force from about 20,000 to about 3,500 today.

But the Balkans operation has become a sort of semipermanent US operation - just the sort of deployment that some conservatives hoped Bush would scale back when he took office. "What is important now is, what does he do in the future?" says Jack Spencer at the Heritage Foundation. "Does he continue to commit us to places that are not really in US interests?"

For the Air Force and Navy, the most deployment-dense area of the world is the Saudi Arabian peninsula and the Gulf. In this region, the US Central Command operates with 30 naval vessels, 175 military aircraft, and upward of 25,000 US service personnel.

The point of all this force is to deter Iraq's Saddam Hussein. But, as military officials note, Saddam is as entrenched in power as ever. Enforcement of no-fly zones is becoming more dangerous. Arab allies of the US are increasingly disenchanted with the United Nations' embargo on Iraq, which they see as more damaging to the average Iraqi than to the nation's leadership.

This is one area where changes in US policy might well bring substantial forces home, says Mr. O'Hanlon of the Brookings Institution. He recommends reducing the naval air presence in the Mediterranean devoted to the operation.

On deployment reduction, "the big debate is going to be Iraq, where forces are really doing something in a tangible way," he says.

Asia also remains an area of substantial US security deployments - and commitments. Some 20,000 of them are Marines crammed onto Japan's island of Okinawa. The Army has 27,000 soldiers in Korea.

Reducing the number of Marines on Okinawa might make sense, says O'Hanlon. He calls them not so much forward-deployed as "marooned." But Asia remains an area of great US strategic interest - and not just because of any perceived threat from an emergent China.

The long-standing US military commitment to South Korea could undoubtedly be cut if relations warm with North Korea. But the North Koreans have so far rejected the Bush administration's insistence that any new talks about closer ties include the issue of conventional armed forces, as well as North Korea's nuclear program.