Amphibious assault vehicle
Amphibious assault vehicle (AAV), also called assault amphibian vehicle, an armed and armored military vehicle designed to deliver assault troops and their equipment from ship to shore under combat conditions. As developed most fully by the United States Marine Corps, AAVs are tracked vehicles that transport troops and material over water and continue to function ashore under hostile fire as logistical vehicles or as fighting vehicles [Encyclopedia Britannica].
The AAV-P7/A1 is the current amphibious troop transport of the United States Marine Corps. It is used by U.S. Marine Corps Amphibious Assault Battalions to land the surface assault elements of the landing force and their equipment in a single lift from assault shipping during amphibious operations to inland objectives and to conduct mechanized operations and related combat support in subsequent mechanized operations ashore. It is also operated by other forces. Marines call them "amtracs," a shortening of their original designation, "amphibious tractor."
The U.S. Marine Corps became interested in replacing the LVTP-5 due to its limited range, slow water speed, and difficulty maintaining the aging platform. In 1964, the Marine Corps solicited proposals to replace and meet its requirement. The Marine Corps selected a proposal by FMC. FMC delivered the first 15 prototypes, designated LVTPX12, in October 1967. Marine Corps testing concluded in September 1969. In June 1970, the Marine Corps awarded FMC a $78.5 million contract for producing 942 vehicles [Foss, p.290].
Amphibious assault vehicle. Encyclopedia Britannica. Retrieved from: https://www.britannica.com/technology/amphibious-assault-vehicle
Foss, C. F., (1979). Armoured Personnel Carriers.London: Jane's Publishing Company.