As expected, Mr. Obama emphasized the symbolic character of Berlin’s history since 1949 as a divided city during the Cold War and then as the starting point for epochal changes since the fall of the Berlin Wall in 1989, that led to the collapse of the Soviet bloc.

“This city, of all cities, knows the dream of freedom. In its darkest hours, the people of Berlin kept the flame of hope burning,” he said, referring to the reunion of the once divided city.

Speaking of that struggle following World War II, Mr. Obama said, “You know that the only reason we stand here tonight is because men and women from both (Germany and the U.S.) came together to work, and struggle, and sacrifice for that better life.”

And he made clear the need for more military togetherness. “The Afghan people need our troops and your troops; our support and your support to defeat the Taliban and Al-Qaeda, to develop their economy, and to help them rebuild their nation.”

The German government has been participating in the U.S.-led war in Afghanistan since 2001, but the German military is not directly involved in war actions. Some 3,000 German soldiers are stationed in the north of the country as part of the International Security Assistance Force to protect civilians involved in reconstruction and to handle logistics such as medical transport.

Besides, six German reconnaissance aircraft and some 500 soldiers are deployed in the violent south-eastern region. The German military is emphatic on its website that the only mission of this contingent is reconnaissance.

This declaration comes in the face of strong public opposition to military involvement in Afghanistan. Some two-thirds of people want German troops out, according to consistent opinion polls. And so Mr. Obama’s call could be an eventual source of conflict.

Earlier, senior foreign policy adviser Susan Rice said in interviews to German media that if Mr. Obama is elected, Europe would have to “uphold responsibilities” in dealing with critical global security challenges.

There are signs that such demands are getting sympathetic hearing. Horst Teltschik, a close aide of former German chancellor Helmut Kohl in the 1990s, said after the Obama speech that “Europeans must again learn that we are not an island of happiness in a troubled world.”

Mr. Teltschik was all but paraphrasing Sen. Obama. In his speech, the U.S. political leader said while the 20th century “taught (U.S. and Europe) that we share a common destiny, the 21st has revealed a world more intertwined than at any time in human history.”

According to opinion polls just ahead of Mr. Obama’s visit to Berlin, 72 percent of Germans would vote for him as the next U.S. president. Through most of his campaign, Mr. Obama has portrayed himself as a liberal. But analysts say Germans may have ignored some positions Mr. Obama took during the campaign, and his recent political turnaround towards more conservative positions.