The historical legacy of 1989, when the Berlin Wall fell and the cold war thawed, is as political as the upheavals of that decisive year....

In general, said James M. Goldgeier of George Washington University, a historian of the period, “the big question out there for 20 years is who gets the credit.”

For many in the United States, he said, most of the credit now goes to President Ronald Reagan and his aggressive military spending and antagonism toward Communism. That view has largely eclipsed another American perspective, which was that globalization and democratization were so powerful that a Mikhail Gorbachev was inevitable, and that the cold war ended through “soft power” — propaganda, diplomacy and the Helsinki accords.

“As the partisan divide over Reagan has dissipated, I think over time most Americans, if they think back at all, say it was Reagan who said, ‘Tear down this wall,’ and down it came,” Professor Goldgeier said.

Robert Kagan, a historian with the Carnegie Endowment in Washington and an editor of The Weekly Standard, said conservatives won the debate. “The standard narrative is Reagan,” he said.

This is not the case in Europe, Mr. Kagan said. “If 90 percent of Americans say it was the U.S. being firm, 99 percent of Europeans think it was they being soft — that the wall fell through Ostpolitik and West German TV.”