U.S. Marine, Jonathyn Smith, a crew chief with 4th Assault Amphibian Battalion, 4th Marine Division prepare ammunition for Assault Amphibious Vehicles on Range 110 during Integrated Training Exercise 4-19 at Marine Corps Air Ground Combat Center Twentynine Palms, Calif., June 7, 2019. AAVs were introduced in 1984 and designed to transport troops in combative environments during sea-based operations. (U.S. Marine Corps photo by Cpl. Tessa D. Watts)