Over the last 12 months, the political and military walls have come down between East and West in Europe. In the last four days, to an extent unprecedented since World War II, the personal walls came down between the presidents of the United States and the Soviet Union.

The central achievement of the summit may have been the one on display for all to see in the East Room of the White House yesterday morning: the extraordinary rapport of George Bush and Mikhail Gorbachev forged in many hours of intense but often very informal discussion. Both men went out of their way to advertise their new closeness.

Gorbachev, in his opening presentation, called this new rapport the manifestation of a "qualitatively new relationship" between the two nations, and he spoke with feeling about his counterpart as "a political leader who is able, in a very human way, and in a politically responsible way to engage in dialogue and cooperation."

"We have moved a long, long way from the depths of the Cold War," said Bush. "I don't quite know how to quantify it for you, but we could never have had the discussions we had at Camp David yesterday or as we sat in the Oval Office a couple of days before that with President Gorbachev, 20 years ago."

To hinge the policy of nations on the personal relations of leaders is a perilous thing, some U.S. officials acknowledged, especially when the Soviet leader is in serious and obvious difficulty at home. Members of the Bush team said yesterday, however, that the rapport at the summit was a sign of something deeper than friendly ties: "an identity of purpose," said one official, "to try to work through any problems that come up and to do so in a fashion that will not damage the overall relationship, even if particular issues don't work out."

Marshal Sergei Akhromeyev, who attended all the summits at Gorbachev's side since Reykjavik in 1986, said yesterday that last week's summit was different from all the others. Until this meeting, the two parties were "if not adversaries, then competitors," Akhromeyev said; now "we are facing quite a new phenomenon." If it is too soon to declare all competition over, he added, it has certainly been greatly reduced, opening new possibilities for cooperative action.

These new underpinnings could be tested in the months ahead, especially in dealing with seemingly intractable issues as Germany's military alignment after unification, which is central to the future of Europe, and the struggle of Lithuania and the other Baltic states to secede from the Soviet Union, which is crucial to the future of the U.S.S.R. Gorbachev has heavy stakes riding on both questions, and his positions today are at odds with those of Bush.

There was no tangible move toward compromise on either of those issues during the just-completed summit, but Bush and Gorbachev seem to have found ways to talk about them candidly and explore the possibility of later shifts without making such imposing problems a test or touchstone of the overall U.S.-Soviet relationship. This appears to represent abandonment of the policy of "linking" Soviet actions in one field to U.S. reactions in others.

Bush's decision on Friday afternoon to sign the U.S.-Soviet trade pact, a reversal of an earlier Bush decision not to do so because of the Lithuania issue, was an earnest of his determination to keep the overall relationship on track despite important differences. Gorbachev made an intense and very personal appeal for the trade agreement as the one item of summit business that could have important political clout with the Soviet people. Bush's decision was depicted by Soviet observers as extremely important to Gorbachev, showing that the U.S. president was willing to support the Soviet leader's perestroika program -- and Gorbachev himself -- even at some political cost to Bush in the United States.

The signing of the trade agreement Friday was by no means the only special consideration shown by Bush to Gorbachev. The American president went out of his way at every turn to discourage the idea that he is dealing with a weakened leader. Regardless of any calculation of weakness or strength, Bush said in the East Room yesterday, he and Gorbachev "have a unique responsibility to deal with world peace. . . . No other countries have the same degree of responsibility that the Soviet Union and the United States have." In another unusual gesture, Bush provided Gorbachev Saturday night with the text of the opening statement he planned to make at their joint news conference yesterday morning, some of it stating bluntly positions at odds with those of the Soviet leader.

All this is light years away from the interaction of U.S. and Soviet leaders from 1945 to 1985 and significantly different from the relationship of Gorbachev with Ronald Reagan, which broke the mold of hostility and thus made history. Philosophically and politically, Gorbachev and Reagan were an odd couple, one a scrappy pragmatist, the other a romantic who dealt in powerful symbols. A Soviet official who came here from Moscow last week recalled Gorbachev's private vow the night before the 1985 Geneva summit to treat Reagan with the respect due to an older man, and he did so throughout four summits and a farewell luncheon in New York.

Gorbachev and Bush, said a senior U.S. official who watched them in intimate meetings here, are much closer to being peers -- "broadly similar kinds of people -- activists, enthusiasts," both with a detailed grasp of political events around the world.

The long road that brought about the extraordinary dialogue of Soviet and American leaders in the East Room, side by side at an antique table, ran through Geneva, Reykjavik, Washington, Moscow and Malta. If U.S.-Soviet summits now become a regular occurrence, as Bush and Gorbachev announced yesterday they would, successive meetings may be less fascinating and spectacular. That assumes, of course, that the new rapport between the formerly hostile powers is more than skin deep.

Staff writer R. Jeffrey Smith contributed to this report.