He had spent the previous months immersed in the history of the Armenian genocide, which occurred from 1915 to 1917, for National Geographic. It was, Mr. Stanmeyer said, one of the most difficult stories in his 30-plus year career.

“I was deeply saddened on a more profound level then I’ve ever been” he said. “I looked at the bridge that used to link two beautiful people and I thought that there had to be something more to do.”

His ambitions were large: nothing less than fostering understanding, ending mistrust and “building peace between two beautiful nations,” he said. But from decades of photographing, he knew that there was “too much madness, indifference and pain” for a single images rarely to bring about significant change. His goals were well beyond what he could accomplish alone.