Photo by U.S. Department of Commerce

On what is his last tour of Europe this week, and what is likely to be his last major tour abroad, outgoing U.S. President Barack Obama has reserved a full two days for Berlin. This unusually long visit to the German capital is not a coincidence. It is here that he first became a figure of global importance when, in July 2008, the then-candidate mesmerized a crowd of 200,000 Berliners. It is here that he developed his strongest rapport with any world leader: German Chancellor Angela Merkel. Most importantly, however, it is here that his foreign-policy legacy now has its strongest, if not last, line of defense.

That Obama would develop this level of political and personal intimacy with the country was hardly obvious eight years ago. In character alone, Obama and Merkel made for something of an odd couple. The charismatic orator met understatement personified. The public intellectual outshined the reclusive scientist. His biography spans the globe; she hails from provincial East Germany. The one roused sky-high expectations; the other was eternally underestimated. And if Obama’s attention was drawn to the rising powers of Asia, Merkel was focused on keeping the Old Continent afloat. It seemed improbable back then that the two leaders would form any bond beyond the polite and professional.