You can thank the US military for the world's smelliest substance

The US military has been attempting to use terrible smells as non-lethal weapons as far back as World War II. We spoke with science writer Mary Roach about the military's decades-long search for the world's worst odor.

You can read more fascinating stories about humans at war in Roach's new book, "Grunt: The Curious Science of Humans at War."

Follow BI Video: On Twitter