"In 1941 Frank Kessler, a young accountant in Canton, Ohio, was drafted, assigned to an Army Signal Corps unit, and went away to photograph the war in Europe. In 1945, home again with his wife and children, he stored hundreds of those images of blood and battle in his attic. There they stayed until after his death.

"Then Lee Kessler, Frank's estranged younger brother, sorted through boxes seeking to better know a brother he'd never known very well. A flier who had been shot down and held in a German POW camp, Lee saw Frank's photographs as images of a different side of war, one he...