Heavy Tanks:
The American M103

By Mike Bennighof, Ph.D.
July 2020

The United States ended the Second World War with a heavy tank, the M26 Pershing, that had just entered service with the U.S. Army in Europe and had been issued to Army and Marine units for the cancelled invasion of Japan. But this tank was no match for the new Soviet heavy tanks that appeared at the end of the war, and was soon classed as a medium tank.

To fill the heavy tank role, design work began on new vehicles even before the war ended. These tanks (the T29, T30, T32 and T34) were derived from the basic Pershing design using many common components, with guns ranging from the 90mm of the Pershing through a massive 155mm gun with two-piece ammunition. None of these advanced beyond the prototype stage.

In 1948, work began on a new tank derived from the T34 (itself derived from the T30), so it still had a family resemblance to the Pershing. The T43 had the same 120mm T53 rifled cannon, a modified version of the M1 heavy anti-aircraft gun, as the T34. It was a huge tank, weighing in at 65 tons compared to 46 tons for the Pershing (though still less than the 75 tons of the German Tiger II).

The T43 carried the same Continental AV1790 power plant as the M48 Patton, then also under development, but was a much heavier vehicle and could only make 21 miles per hour (34 kilometers per hour) while guzzling enormous amounts of fuel, thus limiting its range. It had a cast armor scheme similar to that of the M48, though slightly thicker. It had a gigantic turret, made necessary to accommodate the recoil of its huge cannon. It was, in most respects, a far less capable, though far more expensive, tank than the M48.

An M103/T43 prototype; the heat shield is peeling off the bottom of the turret.

The 120mm rifle provided its lone saving grace. The designers placed great hopes in this weapon, and believed it would allow the new tank to destroy Soviet heavy tanks from well outside their engagement envelope. It could snipe at enemy armor in safety, where its inadequate speed and imperfect protection would not be liabilities.

In early 1951 the Army awarded a contract for 300 of the tanks to Chrysler, which built a new plant in Newark, New Jersey to construct them. The T43 was a “black program,” kept secret from the public and even from those in the military and government deemed to have no need to know. Probably not coincidentally, the program ran into massive cost overruns; a 1957 Congressional audit found that it had cost many times the official $99 million price tag, and huge sums had simply disappeared.

Probably also not coincidentally, the T43 turned out to be a terrible machine. Problems surfaced in its drive train (caused in large part by the underpowered engine), turret controls, gun sights and even in the 120mm ammunition; the giant sniper rifle proved unable to hit its targets. Army representatives told Congress that the program had been a success, since it had delivered tanks in time for use in the Korean War, leaving out the part about them being useless for combat deployment.

The 300 scrap heaps were then rebuilt into a mostly new tank now designated the M103, though the Army continued to insist that these were only minor technical upgrades. Showing its confidence in the machine, the Army foisted 220 of them on the Marine Corps.

An M103 shows off its unusually large turret.

The Army machines went to the newly-formed 899th Tank Battalion, which went to Germany in early 1958 and became the 2nd Heavy Tank Battalion, 33rd Armored Regiment a few months later. Seventh Army commander Clyde Eddleman had asked for the white elephants, hoping that with their long-range accuracy they could provide overwatch for the disappointing early-model M48 tanks equipping his tank battalions. He also expressed concern about the heavy tank’s performance in “retrograde operations” - that is, could the M103 retreat without breaking down. That proved problematic; even with their new and more powerful engines, the M103 remained underpowered for its weight and suffered an unusual number of mechanical failures.

With improved ammunition and upgrades to the cannon itself, the M58 120mm gun proved very powerful and accurate, and tests conducted in 1958 recommended a lightened version for the new M60 main battle tank. But the M58’s two-piece ammunition required two loaders, and the new tank had to have a crew of four rather than the five of the M103. Worse still, the 120mm with an expert crew managed four shots per minute, while the 105mm M68, the American version of the British-designed Royal Ordnance L7, could manage seven with somewhat less penetration performance.

The new M60 could do almost everything the M103 could do (that was part of the design brief, after all), with the greater rate of fire of the 105mm cannon considered a fair trade off for the greater punch of the 120mm gun. When the M60 started to appear in Europe in the early 1960’s, the M103’s very short day in Europe was over. The Army’s heavy tank battalion was de-activated in 1963, just five years after it had been stood up, with the tanks handed over to the Marine Corps. The Marines kept theirs, making upgrades using M60 components including new diesel engines and improved turrets, until they finally received the M60 in 1973 and retired their heavy tanks for good.

One of the last Marine M103A2 tanks prepares to board the LST Saginaw.

The Marines spread their heavy tanks across their tank battalions, with each of the three active and three reserve tank battalions receiving one company’s worth, which still left roughly 100 tanks leftover. None of the Marine tank battalions that deployed to Vietnam took the M103 with them, though they were used on other peacetime training deployments. The Marines appear to have liked the tank, and gladly took the Army rejects, though only 153 of them were upgraded to the final M103A2 standard, hinting that roughly half of the tanks originally built had been consigned to the junkyard and perhaps not enough were operable to equip more than six companies.

The Army’s M103 tanks had been retired by the time of our Panzer Grenadier (Modern) games, Cold War: Fulda Gap 1968 and Vietnam War: Khe Sanh 1968, while the Marines did not take them into action. Our special Panzer Grenadier (Modern): Heavy Tanks expansion set, a special incentive for our Gold Club, lets you use them anyway.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and NASA Journalist in Space finalist, he has published an unknowable number of books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold.