WARSAW — The earth outside the tiny village of Treblinka , in eastern Poland , still bears traces of the death camp the Nazis built there in 1942 . Close to 925,000 Jews were slaughtered at Treblinka , making it the second-largest Jewish killing field in the world after Auschwitz. On a sad, wet day in November, I wandered close to where Germans had burned the bodies of those murdered in the gas chambers nearby. At my feet on the damp ground, among the pebbles, I saw tiny white specks. They were small pieces of bones that still rise to...