On Feb. 1, 1918, a French soldier appeared in the railway station in Lyon. He had lost his memory: He muttered that his name was Anthelme Mangin, but he didn’t know who he was or where he belonged. His uniform lacked unit tags, and his pockets held only a cigarette lighter. The authorities placed him in an asylum and published his photograph in newspapers, hoping that his family would recognize him.

This gave desperate hope to scores of families whose loved ones had disappeared. World War I had claimed the lives of 1.4 million Frenchmen, and 300,000 of their bodies were unidentified or never found. Three hundred families claimed Mangin as their own, and dozens of these were given personal interviews with him. But he responded to none of them.

In 1930 he was identified tentatively as Octave Monjoin, a French waiter in the London embassy of the Ottoman State who had returned to his homeland to fight and been taken prisoner on the western front in August 1914. Judicial officers dropped him off near Monjoin’s hometown and observed him from a distance. He went from the railway station to the village, sat in a café that Monjoin had once enjoyed, walked to the house of Monjoin’s father, whom he did not recognize, and said, “The church has changed.”

But others, who had different hopes for Mangin’s identity, refused to accept the validity of the test, and Mangin remained in official limbo until his death in a French mental institution in 1942 — in the midst of another wrenching war.