Neil MacGregor, soft-spoken and private, finds Germany an endless puzzle and a continuing fascination, a land whose language, art and history have shaped Europe for centuries, and yet remains almost terra incognita for most Britons.

At 69, Mr. MacGregor has long been cherished as one of Britain’s most accomplished cultural figures and has had a strong impact on at least two major institutions. Now, he is leaving the British Museum, which he has transformed as its director, and is decamping professionally to Germany. There, he will help to shape one of that country’s most audacious cultural projects, the Humboldt Forum, intended to frame Germany’s historical and artistic relationship with the world.

He is already considered Britain’s prime interlocutor with Germany. Last year, he curated a popular exhibit, “Germany: Memories of a Nation,” intended to help explain the Germans to the British, and perhaps also to themselves, on themes built around objects and individuals — Luther for language; Dürer for art; the gate of Buchenwald for cultural and political sadism and brutality; the sausage as a symbol of diversity.

The exhibit drew 114,000 people, including Chancellor Angela Merkel of Germany, and an accompanying radio series he did for the BBC, “A History of the World in 100 Objects,” has been downloaded five million times. An associated book with the same title, clearly written and lavishly illustrated, has now been published in the United States.

Mr. MacGregor’s fascination with Germany began as a child, born in 1946 in Glasgow to Alexander and Anna, who were doctors and involved in the war — his father in the navy and his mother in Plymouth, during the severe German bombing of that crucial port. ...