Spidey, a military working dog, performs a controlled aggression technique on the arm of Marine Corps Lance Cpl. Zack Barkley during canine training aboard the amphibious assault ship USS Iwo Jima, part of the Combined Composite Training Unit Exercise in the Atlantic Ocean, Nov. 21, 2017. Barkley is a military working dog handler assigned to the 26th Marine Expeditionary Unit. Marine Corps photo by Cpl. Jon Sosner