A much smaller U.S. military presence in Europe, initially projected for the late 1990s, will become a reality by mid-January courtesy of Iraqi leader Saddam Hussein.

Tens of thousands of the best U.S. troops and hundreds of top-line tanks, artillery and aircraft are being withdrawn from Europe for use in a potential war with Iraq, leaving behind a U.S. force of roughly the size planned for a safer and more stable period years from now, according to U.S. and allied military officials.

The cuts in heavy armament are so large that most U.S. and allied forces in central Europe will immediately come into compliance with a new East-West treaty demanding steep, phased reductions in conventional arms -- more than three years before the Soviet Union is required to meet the same target, the officials said.

The result is anxiety in some European capitals that the U.S. withdrawal may be too disorderly and quick, a fear exacerbated by widespread expectations that many of the U.S. troops and much of the equipment will never return. Some of the forces and equipment may be lost in combat with Iraq. Other troops and weaponry may be left behind in Saudi Arabia as a deterrent to further Iraqi aggression. And some may fall prey to shifting U.S. budget priorities and be shipped straight home, many European defense officials have predicted.

"Everybody {in the North Atlantic Treaty Organization} accepts the necessity the United States is confronted with" in sending forces to the Persian Gulf, NATO Secretary General Manfred Woerner said in a recent interview. "But, of course, some {countries} ask the question, 'How many of them will come back?' "

Although Washington has not yet provided an answer, Woerner said he does not expect all of the forces to return. He suggested that the transfers have pushed U.S. military forces into a downward slide toward a residual force of about 100,000 personnel in Europe, roughly a third of the level earlier this year.

Current plans compress into a few months U.S. reductions that would otherwise have taken place over the next decade, as much of the arsenal created over a 40-year period for a massive land war with the Soviet Union is transferred from snow-covered German bases to the sands of Saudi Arabia.

"This move you are going to see here -- that has already started right now -- is the most significant thing that we have done . . . since we came, starting in 1951 under {Dwight D.} Eisenhower," Gen. John T. Galvin, the supreme allied commander in Europe, said in a recent interview.

The most recent U.S. military unit to head for the Persian Gulf region was the 36th Tactical Fighter Wing of top-line F-15s based at Bitburg, Germany, which left Thursday, more than a week ahead of schedule. In all, squadrons from eight of the 11 U.S. tactical fighter, reconnaissance and airlift wings in Europe are expected to be in the Middle East by mid-January, according to Air Force officials.

This unprecedented shift of air power from the region is matched by a massive transfer of ground forces out of central Germany, roughly equivalent to one U.S. corps of about 75,000 to 80,000 personnel, accompanied by more than 750 tanks, 450 armored personnel carriers, 150 howitzers and 75 attack helicopters. With supporting equipment, the total transfer as of late November -- the most recent public figures -- included more than 20,000 wheeled military vehicles and 4,500 tracked vehicles, according to Army officials.

A force of more than 15,000 of the best troops from the British army on the Rhine, along with 120 British tanks and more than 100 armored personnel carriers, also is being transferred from Germany to the Middle East, British officials said. The reduction amounts to about one-third of the total British forces in Germany allocated to NATO.

To move forces of this size, the U.S. Army has had to displace shipments of German goods on more than 600 German trains and clear entire docks in the Dutch port of Rotterdam and in Antwerp, Belgium, to load ships and barges. A nearly around-the-clock air, land and sea convoy has been established from central military bases in German cities such as Frankfurt, Mannheim, Ramstein and Aschaffenburg to northern and eastern Saudi provinces.

Galvin said he has commanded his personnel to answer, "Yes. What's the question?" whenever contacted by U.S. military commanders in the Persian Gulf under the control of Army Gen. H. Norman Schwarzkopf.

Besides giving up nearly half of his men and fighting machines, Galvin as of November had parted with more than 3,000 sophisticated TOW and Hellfire antitank missiles, nearly 1 million artillery rounds, 500,000 sets of chemical defense equipment and more than 1.5 million "t-ration" prepared meals from Army war reserves under his control, according to Army officials.

Additional U.S. military equipment stored in Europe for an East-West conflict, including more than 60,000 chemical defense masks, 300 jeep ambulances and 690 M-60A3 tanks, has been or will soon be sold to Saudi Arabia, Bahrain and other nations collaborating in Operation Desert Shield, Army officials said. At least six NATO countries besides Germany are helping to transport the U.S. materiel.

"There is a fear {in Europe} that we're in a free fall, that this will just be the beginning," a U.S. military official said. "I think they realize this stuff is not going to come back."

"In a way, it's a convenient excuse," a senior defense official said. "It's like having another engagement when someone insists on your paying a Christmas visit to a relative you'd rather not see as much as you used to."

The resignation last week of Soviet Foreign Minister Eduard Shevardnadze to protest what he termed Moscow's move toward a dictatorship is likely to heighten "short-term anxieties" about the transfers, one official said.

But NATO ambassadors, who met Friday in emergency session in Brussels to discuss the resignation, said in a statement that they expect important elements of Soviet foreign policy, including the phased -- and, in some ways, complementary -- withdrawal of Soviet forces from Eastern Europe, to be maintained under Shevardnadze's successor.

Some of allies' jitters are caused by unilateral U.S. decision-making on which forces will leave for the gulf, officials said. For example, Norwegian Defense Minister Johan Holst met recently in Brussels with Defense Secretary Richard B. Cheney to seek assurances that a U.S. field hospital will be returned to northern Norway when the crisis is over.

"I am . . . convinced that some of the troops that you have recently sent to the gulf will not come back . . . {and} the American contribution to the stability of Europe will be at a lower level {in the future}," said Belgian Minister of National Defense Guy Coeme in an interview. "It shows the necessity to organize ourselves . . . {for} our own security."

Several U.S. officials in Washington said that even after January, the capability of U.S. and allied forces remaining in Europe will more than match that of Soviet forces still deployed in Eastern Europe, including the roughly 360,000 Soviet troops on former East German territory and expected out by 1992.

But Washington has been sensitive to the political consequences of the arms transfer to the gulf region and, for the purposes of the conventional arms treaty, pledged to describe all of the arms as if they had remained in central Europe -- in effect, holding a spot open for their eventual return. "There is still a balance-of-power equation in terms of Europe that has to be kept in mind," Secretary of State James A. Baker III said on ABC News several weeks ago.

Galvin, perhaps reflecting some local anxieties, noted that the transfer of these forces to the gulf, in combination with a congressionally ordered cut of another 50,000 U.S. military personnel in Europe, "is going to take us down to quite low numbers." He said the services were discussing a proposal to obtain a presidential exemption from the reduction.

Cheney similarly told the House Armed Services Committee two weeks ago that "we are in a bit of a paradox -- on the one hand undertaking massive military movement and commitment, preparing for the possibility of hostilities in a major way, while simultaneously preparing a budget . . . that provides for . . . a significant reduction in U.S. military force structure and capability."

Cheney said he may seek relief from the personnel restrictions voted by Congress when he submits a supplemental budget request in late January or early February for Operation Desert Shield. But such a proposal could ignite a fierce debate.

Rep. Patricia Schroeder (D-Colo.), a member of the House Armed Services Committee, said of the transferred troops: "I don't think they're ever coming back {to Europe}. How in the world can we justify our . . . {remaining} there in those {old} numbers?" Sen. John Glenn (D-Ohio), who chairs the Senate Armed Services manpower and personnel subcommittee, said, however, that he was willing to let some of the troops "go back to Europe" if they were not needed in Saudi Arabia and had not completed their normal tour of duty.

Staff writer George C. Wilson contributed to this report.