Marines with Alpha Company, 1st Tank Battalion, scan the horizon with an M1A1 abrams main battle tank during Exercise Desert Scimitar 2014 aboard Marine Corps Air Ground Combat Center Twentynine Palms, Calif., May 11, 2014. A tank’s success on the battlefield is defined by the teamwork of its four crewmen, who each play a vital role. The mission cannot be completed without every member. Each crewman has a specific yet equally important job required to operate the vehicle. (U.S. Marine Corps photo by Cpl. Christopher J. Moore/Released)