Ryan Means was so gung-ho about the military, he ripped out a recruitment card from a magazine, filled it out and mailed it in. A few days later, two Marine Corps officers knocked on his parent’s door in Atlanta, ready to enlist their son. His mother, Mary Jo, sent the officers away. After all, her son was only 9. Young Means revered the armed services. As a kid growing up in Atlanta, he’d frequently don fatigues. At Halloween, he packed heat as G.I. Joe. And every day, he and younger brother Michael would dig foxholes in the back yard, filling...