Amphibious vehicles and tanks plow over mud and grass at Aberdeen Proving Ground, MD

VS soldiers ride in amphibious vehicles over muddy terrain and small pools of water at Aberdeen Proving Ground, MD; includes models with and without canopy in place over driver and passengers' heads / LS amphibious vehicles lead a large tank formation toward camera over hilly, grassy and muddy terrain / VS tanks cross hilly and grassy terrain to muddy road / MS tanks roll over muddy road, hills, trees and grass in background / MS armored trucks pull heavy artillery cannons / PAN LEFT tanks rapidly descend grassy hill, one knocking over a tree / VS tanks ride over muddy paths at high speed, pass camera / MS jeep drives into deep muddy pool and gets stuck, amphibious vehicles pass thru on either side of it / MLS two amphibious vehicles, one with top up, plow over muddy ground toward camera / MS amphibious vehicle with top up plows thru mud / VS amphibious vehicle with top down does same / Note: exact year not known; documentation incomplete