Members of the British Royal Marines toss simulated grenades during an obstacle course on Del Valle Field aboard Marine Corps Air Ground Combat Center, Twentynine Palms, Calif., Oct. 7, 2014. U.S. Marines, Dutch Marines, and Royal Marines were competing in the Combat Center's High Intensity Tactical Training Black Alligator Challenge. (Official U.S. Marine Corps photo by Staff Sgt. Leon M. Branchaud/Released)