Original sentence: Heinlein wrote the fictional novel "Sixth Column" in 1949, extending the concept of the fifth column to include instead a hidden army of patriots fighting an oppressive occuppying force of Asians on American soil, distinguished from the "fifth column" of "traitors" within Spain
Edited sentence: Heinlein wrote the fictional novel "Sixth Column" in 1949, extending the concept of the fifth column to include instead a hidden army of patriots fighting an oppressive occuppying force of Asians on American soil, distinguished from the "fifth column" of traitors within Spain