M103 (Tank, Combat, Full Tracked, 120-mm, M103) Heavy Tank
The M103 Heavy Tank was the culmination of American World War 2 tank experience and appeared only after the Korean War, living a relatively short service life primarily through the USMC.
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The M103 (formally designated as "Tank, Combat, Full Tracked, 120mm, M103") was a heavy tank design of American origination developed to counter the threat posed by the growing number of Soviet systems in use during the early stages of the Cold War. Development began during World War 2 though the project would not come to fruition until the end of the Korean War. The M103 managed a relatively short service life and saw service primarily with elements of the United States Marine Corps though the US Army proved the other notable operator in lesser numbers. No more than 300 units were ever completed and the rise of the Main Battle Tank ended the reign of the dedicated Heavy Tank for the foreseeable future. Designs such as the M103 undoubtedly paved the way for the MBT and proved the necessary stepping stone in the genesis of the modern fighting tank we know today. Many examples exist today as showpieces throughout the United States. A foreign example survived at the famous Bovington Tank Museum in the United Kingdom.
The massive tank clashes that permeated the World War 2 battlescape ushered in all-new developments during the conflict. For the Americans, its star performer became the ubiquitous M4 Sherman with its 75mm main gun, an armament not quite on par with contemporary offerings in Britain, Germany and the Soviet Union but nonetheless adequate. While Shermans were eventually handed the improved 76mm main gun, the M36 Tank Destroyer fielded the evermore powerful 90mm main gun in its open-topped turret and was designed exclusively as a tank destroyer. This proved timely with the arrival of considerably heavier, stouter and more powerful German tanks in the Panzer V "Panther", Tiger I and Tiger II series - the latter two classified as heavy tanks. The Americans were therefore forced to develop heavy-class tanks in turn to help counter the improved armor of the enemy. Additionally, advancing into German-held territories would also call into play fortification-defeating gunnery platforms which was also under consideration by the Allies on a variety of levels.
By the end of the war, the culmination of American tank engineering produced the M26 Pershing Heavy Tank with its 90mm gun and thick armor - a vast improvement over the wartime Shermans. However, these managed only a small role during the final weeks of World War 2 in Europe and were not in play before the fall of Japan in the Pacific. Other imposing heavy tank projects such as the T29 and T30 eventually fell to history leaving the M26 and the various M4 Sherman variants as the primary spearhead of the American army. After the war, the M26, which was initially classified as a heavy tank, was reduced to a medium tank categorization due to a US Army weight restructuring. Many of the earlier M4 Sherman marks were also deemed obsolete as soon as 1946, leaving just the 76mm-armed variants in inventory and reducing capabilities of the US armored corps considerably. At any rate, as the world now fell into a Cold War against the mighty Soviet Union and its legions of tracked armored vehicles, the US armored inventory was woefully under-equipped to combat such beastly creations as the 122mm-armed "Josef Stalin" heavy tank of the Red Army - the IS-3 alone showcasing armor protection some eight inches thick.
The challenge to American vehicle designers now fell on devising a perfect "dual-role" tracked system capable of engaging enemy armor at range while also being able to defeat fortified structures. During World War 2, this largely fell to two different vehicle types which proved logistically unsound in the long run. With the United States Army and Marine Corps now in desperate need for a multirole gunnery platform sporting inherent mobility and strong armor protection, engineers certainly had their work cut out for them. All of this wondering this led to the "T34" proposal which sought to fulfill all of the listed requirements in a single, relatively affordable package. Design work on the new initiative began in 1948.
The T34 plan was then modified to reduce the standard operating crew by one to five personnel. There was a reduction in the proposed vehicle's operating weight to 58 tons which would, in turn, could theoretically provide the needed mobility. Armor protection would reach up to five inches across critical frontal facings and the main gun of choice became a 120mm system recognized under the T122 designation. The weapon was based on a wartime anti-aircraft gun and modified to become the T53E1 in the new design. This long-barrel assembly would be fitted to a heavily sloped and thickly armored turret with a full 360-degree rotation. The chassis was conventional with wide track links, seven double-tired road wheels to a side and a rear-set drive sprocket with forward-mounted track idler. No fewer than six track return rollers were be utilized. The engine was set in a rear compartment while the front of the hull was well sloped with a thick layer of cast armor. A massive T-style muzzle brake would cap the gun. Power would be provided by a Continental AV-1790 12-cylinder, gasoline-fueled engine outputting at 750 horsepower. The T34 proposal was then evolved to become "T43" by December of 1948. A formal request for development - and subsequent production - was signed in May of 1949. Pilot (prototype) vehicles would precede the production models for both the US Army and Marines for evaluation purposes and these would all be led by a wooden mockup which was studied extensively. Some 276 total T43 Heavy Tanks were slated for procurement though this would eventually be affected by outside changes influenced by the political and budgetary landscape.
By this time, the T43 program had begun to streamline itself for ease of production. Many technology-heavy aspects of the original design were dropped including remote-controlled external machine guns, computer assisted fire control and an automatic loader (which increased the operating crew to five personnel). In June of 1950, the communist forces of North Korea invaded the democratic South and brought upon the world its next major war - the Korean War (1950-1953). This placed the obsolete M4 Sherman marks and outdated M26 Pershing marks back into combat while also threatening the future of the now-costly T43. Engineers responded by delivering the M26-related M46 Medium Tank series for the interim while the T43 program managed to survive consistent threats to its very existence.
Instead of certain death, the T43 was progressed through an official order for 80 tanks requested by US Army to shore up its outdated stocks in December of 1950. The USMC sought a long-term replacement and engaged in a production order for 195 vehicles to which the total then grew to 220 requested units in 1951. In June of 1951, the initial T43 pilot vehicle was completed by Chrysler out of its Newark, Delaware facility and made ready for formal evaluations at the famous Aberdeen Proving Ground in Maryland.
The new design quickly showcased a myriad of technological and mechanical issues that required serious attention. Changes were requested that included increased armor protection which, in turn, increased operating weights and led to a reduction in speed. The main gun was updated to the 120mm T123E1 and more subtle changes greeted the internal fighting compartment. Testing was hurried which overlooked existing issues not entirely ironed out in an effort to have the tank ready for service in the Korean War. After passing the requisite Army tests, the vehicle was formally accepted for serial production under the "T43E1" designation.
The T123E1 main gun offered considerable fire power at range over that as seen by the upgunned M4 Shermans, the M26 Pershings and the M46 Pattons. It was designed to fire a 32lb High-Velocity, Armor Piercing (HVAP), a 23lb Armor-Piercing Discarding Sabot (APDS) and a 50lb Armor Piercing Capped (APC) projectile at a muzzle velocity of 3,300 to 4,200 feet per second depending on projectile in question. This allowed for penetration of 13.5 inch armor or less at ranges out to 1,000 yards. Of course the size of 120mm projectiles within the tank turret and hull limited total available projectiles carried. While mobility was lacking, the design certainly could give the Soviet offerings a challenge at the ranges expected in both Korea and Europe. Original M103 models were given 2 x 7.62mm coaxial machine guns while the later M103A1 introduced only a single fitting. A 12.7mm Browning M2 anti-aircraft gun could be fitted to the turret for close-in defense. The M103 housed 38 ready-to-fire 120mm projectiles, 5,250 rounds of 7.62mm ammunition and 1,000 rounds of 12.7mm ammunition.
Production of the T43E1 was underway in December of 1942 and would continue into June of 1954 by which point the war in Korea was over through an uneasy armistice. The T43E1 was adopted into the US military inventory as the "M103" with no nickname ever being assigned. Total production netted 300 examples from the Chrysler Newark plant.
The hasty arrival of the M103 necessitated additional modifications heading into 1956 with a pair of T43A2 pilot vehicles to serve as needed testbeds for evaluation. M103s were shipped to Europe to manage strategic chokepoints against an impending Soviet ground invasion. The US Army charged 74 for improved modification and these were then returned to active service. However, the USMC required even more in-depth changes to their M103s before it could be operationally introduced with computerized fire control and a revised turret. Based on the T43A2 prototype, the USMC eventually accepted 220 USMC M103s under the new designation of "M103A1" with deliveries occurring in January of 1959. 219 M103s were either converted or rebuilt to this new standard. US Army M103s arrived in Europe to the 899th Heavy Tank Battalion of the 7th Army, replacing their M48s then in service. Ironically, the US Army then requested, and was approved, to receive 72 M103A1 units from the USMC stock. These tanks joined their brethren in May of 1959 and maintained their positions until 1963 to which they were handed back to the USMC.
While the US Army had all but given up on the M103 by this point, the USMC soldiered on with the M103 as their heavy tank for the foreseeable future. The "MBT-70" joint tank program between the United States and Germany was to usher in the next generation of American fighting tank. However, prior to its arrival, there would have to be a period fulfilled with a low-cost interim solution. Instead of acquiring the US Army's latest Main Battle Tank - the M60 Patton - the USMC elected to installed M60 components to their existing M103 line. This included use of the same Continental AVDS-1790-2A diesel engines coupled to and all-new internal fuel stores. The modernization program began in August of 1963 with deliveries of the new systems in May of 1964. The M103A2 proved a noticeable upgrade to the M103 line as a whole with both operating speeds (23mph from 21mph) and operational ranges (300 miles from 80 miles) both increased. The M103A2 shared much of the same automotive components and rangefinding equipment as the M60 MBT and 153 examples were either rebuilt or converted for need.
The end of the line for the M103 came in 1972 when all existing units were retired from USMC service. The type was completely out of circulation by 1974. Left without a viable tank option (the MBT-70 program fell to naught and the M48 was highly outdated without the prospect for modernization), the USMC was forced to procure the US Army M60 MBT in number. The M60 replaced all existing USMC mounts from there on and remained the standard USMC main combat tank for the decades precding the arrival of the M1 Abrams.