In America, 1918 was a time of idealism and duty. Young men joined the military, eager to fight the German menace. Women raised money to support the troops and worked in munition factories. Patriotism was at a fevered pitch.

            But not everyone believed in the rightness of war. Leslie Hotson’s conscience led him to go to France with the American Friends Service Committee to repair the wounds of war. Mary Peabody worked to change conditions at home as a radical...