KENNEBUNKPORT, MAINE, JULY 3 -- Two months ago, President Bush tried to explain to an audience of graduating college students why they should care about "a continent 4,000 miles away . . . our neighbors across the Atlantic."

Ticking off the string of European upheavals that had drawn Americans to battle, Bush spoke of World War II, in which he fought as a pilot, and of the importance of the postwar order put in place.

His generation of Americans, Bush said, had paid "an awful price, a horrible price" for the earlier U.S. isolation from Europe. It is not a generation that asks what Europe has to do with them, he said, "because they knew the answer -- everything."

The formation of the North Atlantic Treaty Organization was one of the principal results of that experience, and for 41 years it has welded the United States and Western Europe into a community of shared interests and mutual defense.

Bush flies to London Wednesday night for a summit meeting of NATO's 16 heads of government. Yet in the little more than a year since they last met, the world order created after World War II has changed almost beyond recognition, with the collapse of the Soviet empire and the Warsaw Pact, the emergence of freely elected democratic governments in Eastern Europe and the rapidly approaching complete unification of Germany.

"This is one of the most important NATO summits that will have been held in the history of the 40-year alliance," Secretary of State James A. Baker III said today on his way to Brussels for a day of talks with other foreign ministers on future economic aid to Eastern Europe.

For the United States, according to top Bush aides, the broad goal is to maintain U.S. leadership and influence in a Europe in the throes of breathtaking change, while reassuring the Soviet Union that the new Europe will be a stable, non-threatening neighbor and a force for cooperation, not aggression.

Bush, who called for this special NATO session last May, said today that its purpose should be to "launch a wide-ranging NATO strategy review for the transformed Europe of the 1990s." He said he hopes that a series of proposals he has made to NATO let "everybody understand NATO is the stabilizing factor that we think it should be and will be."

Senior U.S. officials said there would be no attempts to conceal the aim of securing Soviet acquiescence to a unified Germany in NATO. "If there are certain things we can do to expand NATO's role that drive that point, so much the better," Bush said.

Earlier this week, the president said he had no "bombshell" announcements to help achieve his goals. The plateful of proposals he will take to London have been quietly circulated in European capitals in recent days.

They include:

A formal pledge of nonaggression from the Western alliance to member nations of the disintegrating Warsaw Pact, which closely tracks longstanding NATO defensive policy.

A clear Western promise that U.S. tactical nuclear weapons in Europe will be used only as a last resort in responding to a Soviet conventional attack, modifying current NATO policy that in theory permits an earlier use of such weapons.

New arrangements for Soviet and other East European representatives to observe periodic NATO headquarters discussions in Belgium. Establishment of a permanent staff and a regular schedule of meetings for the 35-nation Conference on Security and Cooperation in Europe, a loose-knit organization that the Soviets have said should be the principal forum for deliberations on European security.

The restructuring of West German and allied military forces to enhance their subordination to multinational commanders and to thin out troops at the East European border.

A new U.S. pledge to withdraw eventually all short-range, nuclear-tipped artillery shells now deployed in West Germany and four other nations, none of which will have sufficient range to hit important enemy targets once Soviet troops are withdrawn from the region.

U.S. officials said in interviews that the aim of changes is to refine NATO doctrine in a way that would create new political support for the preservation of as much of the organization's existing structure as possible. Although the Warsaw Pact has disintegrated, the United States intends to press for continuation of the integrated NATO military command, including forces in a unified Germany.

The leaders are not expected, for example, to jettison the Cold War doctrine of "flexible response" to Soviet aggression, including the possible first use of nuclear weapons if necessary to counter superior Soviet conventional forces, despite the Bush proposal that the doctrine be modified to say such weapons would be used only as a last resort. That formulation leaves room for potential new U.S. nuclear weapon deployments, the officials said. National security adviser Brent Scowcroft said today that the administration opposes any declaration that NATO will forswear the first use of nuclear weapons. "Conventional deterrence is an inadequate reed to lean on," he said.

The administration's calculus in making such decisions is essentially that more sweeping Soviet-backed proposals for reforming the two military alliances can be given short shrift without significant political risk, and that "new paint can be put on old {NATO} siding," as one official said, to give Soviet President Mikhail Gorbachev sufficient leverage against his conservative critics at home.

The U.S. judgment reflects what officials consider the lopsided nature of recent European political reforms, which swept six nations out of Moscow's orbit and drew them toward the West. As Defense Secretary Richard B. Cheney said recently, "The Warsaw Pact is going away," sharply scaling back the Soviet empire, while NATO remains "the mechanism by which we participate in European security."

Undersecretary of Defense Paul D. Wolfowitz said in a recent speech that "we can now view as nearly certain the withdrawal of {all} Soviet forces from Eastern Europe," not just those leaving Hungary and Czechoslovakia next year. Several senior U.S. officials said they were increasingly confident that U.S. forces will not likewise be quickly forced from German territory, giving the United States an upper hand in bargaining with the Soviets.

Sen. Joseph R. Biden Jr. (D-Del.) disagrees with this view, on grounds that Moscow can heavily influence the degree of German public support for NATO membership, and so should be given additional guarantees that would effectively quiet their troublemaking. He urges an allied declaration that "the military rationale for the first use of nuclear weapons has disappeared, and simply saying so would enable us to reap substantial political gains in Germany and Moscow."

But many alliance officials say such a move is not necessary at the outset of a strategic review that may not be completed until 1992, and remain optimistic that they will have done enough by the close of the summit to win Soviet acquiescence to German membership in NATO.

One senior U.S. official traveling on Baker's plane today to Brussels, who declined to be identified, said that the United States wants to see a "serious" Soviet response, unlike "the sort of pro forma Politburo response" offered by Moscow at the last special meeting of foreign ministers to discuss German unification.

The official was referring to a series of detailed Soviet conditions that the West has deemed unacceptable, including a low ceiling of roughly 200,000 to 250,000 troops in the unified Germany, less than half the current total. He predicted that the West will withhold a counteroffer on the issue of limiting German troops until the Soviets had eased this demand.

Such Soviet requests raise questions about whether the new Western measures will be enough to satisfy Gorbachev and his restive populace, including conservative critics asking, "Who lost Eastern Europe?" German officials have suggested that long-term prospects of more substantive NATO reforms, combined with immediate infusions of cash to the starved Soviet economy, will overpower Soviet political concerns.

But Soviet Foreign Minister Eduard Shevardnadze has suggested a tough standard for measuring the summit's success in transforming the Western alliance. "We should realize that what matters is not only its direction but also, to a greater extent, the dynamics and magnitude of change," he said, suggesting that the promise of an ongoing strategy review is not enough.

Devroy reported from Kennebunkport. Smith was traveling with Baker.