Staff Writer (Updated: 6/23/2016):
Roebling delivered the first incarnation of his civilian design with the "LVT-1" and production by Food Machinery Corporation began soon afterwards in 1941 with 200 contracted vehicles. The LVT-1 sported a top speed of 12 miles per hour and armament was either 2 x 0.30 caliber general purpose machine guns or 2 x 0.50 caliber heavy machine guns mounted on rails or pintle mounts with optional limited shielding. Troop capacity was 18 to 24 combat ready soldiers. After some experience, four guns - two of each type - were being fitted forward and aft of the loading area for maximum support defense. Power was derived from a single Hercules WXLC-3 engine. Some 1,225 examples of the LVT-1 series were ultimately produced. It is of note that LVT-1 series models were not armored in any way beyond their factory "skins" and were generally intended as resupply vehicles.
The LVT-1 was modified with the next variant, the LVT(A)-1 of 1942 ("A" signifying "Armored"), to serve as a fire support vehicle with the installation of an M3-style tank turret (37mm gun), rear-mounted machine guns and armor plating. The engine was changed over to a single Continental W970-9A series but remained largely faithful to the original LVT1. A total of 510 examples were delivered. However, the LVT1 production model was still too closely tied to its civilian roots to make it an adequate "weapon of war" for the sake of amphibious assaults. Armor protection was still too thin for comfort and maintenance issues grew over time to make critical systems quite unreliable. These issues required the LVT to undergo further refinement.
The first truly notable LVT development came next with the arrival of the LVT-2 ("Water Buffalo" / "Buffalo II") in 1942. This production version revised the general hull shape to more closely mimic that of a boat for improved water traversal. A new suspension system was introduced for better terrain capability and bolt-on aluminum track grousers were installed for ease of maintenance and repair. As the M3A1 Stuart light tank was in full production by this time, it made logistical sense to utilize its existing components - namely the powertrain - in the revised LVT-2. The engine was now relocated to the back of the hull with the crew cabin moved to the front. The onboard arrangement then left the central portion of the hull to be hollowed out and used for cargo or passengers (this area was still left "open-topped"). However, this revision led to a few inherent restrictions - namely, the centralized location of the loading area restricted the LVT-2 to carrying just infantry and some light equipment with applicable supplies. Since there was no loading ramp, infantry would have to scurry off the vehicle over the hull sides under their own power in full combat gear, utilizing precious energy in the process while exposing themselves to the risks of the modern battlefield - risks such as machine gun and small arms fire. Vehicles and valuable towed artillery pieces, therefore, could not be carried in such a space restricted with only a topside entry/exit access point.
The LVT(A)-2 of 1943 was nothing more than an LVT-2 production variant with armor protection. Troop capacity was eighteen and some 450 examples were produced.