Commandant Gen. Jim Amos and Sergeant Major of the Marine Corps Mike Barrett visited Johns Hopkins Hospital in Baltimore last week, intent on seeing Army Sgt. Brendan Marrocco, the first American serving in Iraq or Afghanistan to survive a quadruple amputation. As I outlined in this feature story, the trip renewed a friendship between the commandant and the soldier, a wise-cracking infantryman with an (unfortunate) love of the New York Yankees. In December, he became the first veteran of this generation’s wars to receive a double-arm transplant, and he has pushed hard with his physical therapy since. Marrocco doesn’t yet…