Berlin, Germany | AFP |.US President Barack Obama and German Chancellor Angela Merkel may have got off to a rocky start but his impending departure has sparked a wave of nostalgia and trepidation in Berlin.
As Donald Trump threatens to upend the pillars of the postwar order, few cities have historically symbolised the strength of the transatlantic bond more than the reunified German capital, where Obama held the biggest rally of his 2008 watershed campaign.
Although Merkel barred him from speaking at the Brandenburg Gate, deeming the landmark of German unity too presumptuous a backdrop for the young senator, Obama drew 200,000 cheering fans to the nearby Victory Column monument for a speech about ripping down walls of division.
Now, as Berliners prepare to bid him goodbye, many say Obama left relations far better than he found them, making the impending presidency of Trump who is sworn in Friday a source of widespread anxiety.
"Merkel and Obama are both 21st century leaders, not only because she was the first woman as chancellor and he was the first black president, but because of their modern, intelligent, far-sighted approach," said Antje Pohle, a 33-year-old public relations executive.
"Obama wasn't perfect but he will be missed in Berlin, especially when you look at the Trump insanity."
Clemens Doepgen, 50, who works at US automaker Ford's German unit, predicted "very tough" negotiations on trade, dismissing Trump's protectionist rhetoric as "crude and simplistic".
"America under Obama was a reliable partner -- Trump's erratic approach could be very bad for business."
- Tectonic shift -
In his 2008 address, Obama used the once-divided city's rebirth as a symbol of progress, placing himself in the ranks of former US presidents who saw Berlin as a crucible of epic struggles.
Just months before his 1963 assassination, John F. Kennedy delivered the stirring declaration "Ich bin ein Berliner" (I am a Berliner) to 450,000 people when West Berlin found itself on the frontline of the Cold War.
It offered a crucial message of reassurance a year after the United States and Soviet Union nearly went to war in the Cuban missile crisis, and two years after East Germany's communist regime erected the Berlin Wall.
Obama's speech was also a clear echo of Ronald Reagan's call to then Soviet leader Mikhail Gorbachev in Berlin in 1987 to "tear down this wall". Two years later, the Cold War barrier would be toppled in a bloodless revolution.
Obama and Merkel, who took power in 2005, developed a strong partnership, despite rifts over revelations of NSA spying on Merkel's mobile phone and Obama's vocal opposition to Germany's austerity-driven response to the European debt crisis.
During Obama's tenure, the US and Germany, along with the EU, racked up a series of policy agreements that Trump has now thrown into question, including the Iran nuclear deal, the Paris climate accord and economic sanctions against Russia over the Ukraine crisis.
But more fundamentally, Obama's time in office saw a tectonic shift in transatlantic relations.
"For so long in the post-war period Germany was kind of a protectorate -- at least West Germany -- and even after the Wall fell, it was still somewhat of an adolescent. But I think Obama has seen Germany come of age," Sudha David-Wilp, senior transatlantic fellow with the German Marshall Fund of the United States, told AFP.
"At the end of his two terms, we've seen he has come to rely on Chancellor Merkel for advice and discussions and how Germany has come to be seen as an indispensable partner. Germany has come to assume more responsibility in the world and sees itself as a power for good."
- 'Audience that claps' -
On a farewell visit to Berlin in November, Obama praised Merkel as an "outstanding" ally, as the two leaders stressed the need for a strong NATO, free trade and action on climate change.
Trump's inauguration could trigger a dramatic about-face, as he declared in an interview with European newspapers Monday that NATO was "obsolete", the European Union purely a "vehicle for Germany", and Merkel's welcome for refugees a "catastrophic mistake".
Despite the obvious break with Washington policy and tradition, outgoing US ambassador to Germany John Emerson said Trump would be wise to seek "common ground" with Berlin.
"Right at the beginning, he should visit the place his family came from," Emerson said, referring to Kallstadt, the village in the wine country of Germany's southwest where his paternal grandparents were born.
After Obama's two rapturously received addresses in Berlin -- the second in 2013 when Merkel finally offered him the Brandenburg Gate as a venue -- Emerson advised Trump not to set his sights so high.
"It will take some time before he gives a major speech here (in Berlin). After all, you want an audience that claps."