The clock on Buchenwald’s entrance is stopped at 3.15; the moment on April 11, 1945, when US soldiers liberated the concentration camp and had their first encounter with the Holocaust.

Time slowed down, too, for President Obama yesterday as he made his way along gravel paths, past the watchtowers and barbed wire, to the ovens that were used to dispose of those murdered by the Nazis.

The aim of the two-hour stopover on his way to the D-Day beaches was to affirm his bonds with Israel — despite his criticism of the settlers, and the slight hardening of tone in his Cairo speech to the Muslim world on Thursday. The aim, also, was to put down the Holocaust deniers such as President Ahmadinejad of Iran — and this the US leader did with brisk efficiency. When the camp was freed, he said, General Dwight Eisenhower forced local Germans to view the corpses so that the horrors could not later be dismissed as war propaganda.

“This work is not yet finished,” said Mr Obama. “To this day there are those who insist that the Holocaust never happened.”

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The lowest point of degradation to which humanity has descended

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Accompanied by Angela Merkel, and guided by Elie Wiesel, the Nobel Peace Prize winner, the President laid white roses around the sprawling camp compound. More than 56,000 people died in the camp, which housed Jews, political prisoners, homosexuals and the one black man in the Nazi camp system, Gert Schramm.

Mr Obama’s great-uncle, Charles Payne, took part in freeing the camp, but the President’s speech was resolutely political — until Elie Wiesel began to speak. Then the President and the German Chancellor appeared to choke back tears. Mr Wiesel was a 16-year-old boy in Buchenwald.

“I came to visit my father’s grave,” said Mr Wiesel, “but he has no grave.” The writer then went on to describe the day that his father died. “I was there when he suffered, when he asked for help, for water,” he said. “But I was not there when he called for me, though we were in the same block; he was on one of the higher bunks, I on the lowest. He called my name and he died and I didn’t come. I was too afraid.”

Suddenly the two leaders started to fidget. They had made respectful, well-intentioned statements, emphasising the impossibility of language to describe the atrocities committed in Buchenwald. But Mr Wiesel found the words. “So I thought I would come back and speak to him, my father, about the world that has become mine,” he continued. “What could I tell him? That the world has learnt? I’m not so sure.”

This, Mr Wiesel indicated, should be a defining moment for President Obama: the moment in his presidency when he realised that he had a duty, not only to the living but also to the dead, to conciliate enemies.

The President abandoned his lawyer-like formality and kissed Mr Wiesel on both cheeks. Mrs Merkel awkwardly followed suit. She was later given a handkerchief.

The Obama trip has been carefully orchestrated, symbolic gestures and locations all carefully woven together. Buchenwald was important to balance the conciliatory words delivered to the Arab world on Thursday — but also as an integral part of a tour that was supposed to say something about the President’s attitude to war; its heroic episodes, its victimhood, and the necessity to go into battle as a last resort in the name of humanity.

After leaving the camp, the President flew to the US military hospital in Landstuhl, in western Germany, to visit soldiers wounded in Iraq and Afghanistan. At the D-Day ceremonies he was expected to deliver words about the need to fight and put one’s life at risk to defeat tyranny.

He needs to persuade an increasingly sceptical US public that the war in Afghanistan should be stepped up — and the trip to Europe is supplying some of the historical imagery.

Buchenwald was a building block in the visit. After Mr Wiesel’s passionate outburst it could become more than that; a reference point in a still-young presidency.

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