They spent their childhoods in the rich, layered Jewish life of prewar Poland, then survived Hitler's mission to wipe out European Jewry in the ghettos and gas chambers of occupied Europe. Now, men such as Tad Taube, Sigmund Rolat and Severyn Ashkenazy have returned to Poland as philanthropists — after making fortunes in the United States — to nurture a grass-roots revival of Jewish life in their homeland. And while some Jews in America and elsewhere cannot comprehend why the philanthropists choose to return to a land where their ancestors suffered such pain and loss, members of Poland's Jewish community...