Grunt tackles the science behind some of a soldier's most challenging adversaries—panic, exhaustion, heat, ​flies, ​noise—and introduces us to the scientists who seek to conquer them. ​Roach ​​visits a repurposed movie studio where amputee actors help prepare Marine Corps medics for the shock and gore of combat wounds. At Camp Lemmonier, Djibouti, in east Africa, ​she discovers that diarrhea can be a threat to national security. Back in the US, fashion design​ers at U.S. Army Natick Labs​