As World War II’s reluctant allies became Cold War adversaries, the United States found itself facing multiple – and decidedly different – combat scenarios for tank warfare. The primary focus remained on the “cold” front, where U.S. and NATO forces faced thousands of Soviet and Warsaw Pact tanks in Europe. But Korea – and then Vietnam – provided extremely different environments, enemy forces and tactics on “hot” fronts in which the Soviet Union did not commit itself to direct conflict with the United States.

To the dismay of many veteran tankers in the 1950s, two new, fast evolving technologies were being touted by the Eisenhower administration to quickly – and more cheaply – counter the Soviet/Warsaw Pact European theater superiority in numbers and types of armor: Battlefield nuclear weapons and rockets and missiles.

“The administration recognized early on there was no way in time of peace, after Korea, you could sustain wartime mobilization of industry and the population – not in terms of cost or political support – without a real shooting war. Atomic weapons were a less costly means of keeping the Soviets at bay,” said Dr. Robert S. Cameron, Armor Branch historian at the Army Armor Center at Fort Knox. “Ground forces in Europe, however, still had to defend West Germany, so the focus there remained on armor, armored divisions and the forces involved with that.”

Also high on the list for ground forces was a new look at what armor had to do in combat and what kind of technologies were needed to overcome the West’s numerical disadvantage.

“The design focus in the mid 1950s was simple – identify the target as far away as possible, then acquire, engage and kill it, preferably with one shot. To do that, you needed better optics, fire control systems and ammunition. But with basically the entire national defense establishment embracing atomic weapons, those wedded to more conventional concepts often had trouble getting funding,” Cameron said.

“It was a very evolutionary process, moving from the M46 to the M47, then the M48 and, by about 1960, an M48 upgrade called the M60. There wasn’t a lot of fundamental change, just component upgrades. The M48, for example, introduced a ballistic computer and better optics, in line with acquiring targets at a greater range. At the same time, you also had people working on a revolutionary path of development, trying to incorporate missiles, rockets, different platform configurations and other new technologies. Most of these designs never got out of prototype.”

One new U.S. tank that did emerge from the 1950s was the M551 Sheridan, a light tank designed to replace the M41 as an Armored Airborne Reconnaissance Assault Vehicle.

“If you put a bunch of lightly armed paratroopers behind the enemy, how do you protect them if counter-attacked by a heavy armor force? The answer was some mobile anti-tank capability of their own,” Cameron explained. “Combine that with growing experimentation in missiles and rockets and you get the Sheridan, which mounted a gun missile system – the Shillelagh – on a relatively light aluminum chassis.

“The Shillelagh was capable of destroying any known main battle tank on the planet at pretty respectable distance. Put that on a light armored platform and you have a powerful weapon system that can be air-dropped and, when not firing a missile, you have a 150mm gun tube that also can fire a 152mm conventional round. So from the armor standpoint, it’s wonderful – light, air-droppable, state-of-the-art anti-tank protection and an incredibly powerful bunker-busting, canister-throwing conventional weapon system.”

The Sheridan entered service in the 1960s and was fielded to Vietnam around mid-decade as part of President Lyndon Johnson’s massive increase in U.S. presence there. While it initially suffered from limited funding and an increasingly long concept-development-fielding chain, it also benefited from the Kennedy/Johnson administrations’ shift away from a near total dependence on atomic deterrence and the decision to add a powerful conventional deterrent, as well. That increased funding for a more flexible response to the ingrained Cold War view that Soviet mechanized capability was constantly increasing.

“With a return to conventional systems and working to improve them, the M60 was fielded in greater numbers, the M48 went through multiple upgrades and the Army shifted finally from gas to diesel engines, providing greater operational radius to tanks,” Cameron said. “Throughout this period, the focus was still on Central Europe and dealing with the Soviet horde. There was not a lot of attention in the early Sixties on other parts of the planet – such as Southeast Asia – by the armored community.”

Although the U.S. sent armor advisors to South Vietnam to help them establish their own armored force, the U.S. Army did not see a real role for American armor in that war prior to 1965. However, experiments with armored cavalry in Germany had demonstrated its potential area security role against saboteurs, guerillas and airborne attack. That led to the development of some basic concepts on how to use an armored cavalry regiment in a counter-insurgency (COIN) role.

As the large-scale U.S. ground build-up got under way in Vietnam, debate continued on whether its jungles and rice paddies were appropriate terrain for armor or mechanized infantry. Indeed, the first tanks deployed there essentially were limited to perimeter guard duty around major fixed facilities.

“Two things ultimately overturned that policy – the experience of U.S. advisors with Soviet armor units in the early 1960s provided practical experience in how to use armor units in all areas of Vietnam, including jungles and rice paddies,” Cameron said. “Second, the units themselves and their commanders began to develop their own TTPs (tactics, techniques and procedures) on how to operate. What armor brought to Vietnam was the ability to move, engage just about any target and provide a great deal of armor protection.”

As U.S. armor began to encounter Viet Cong and North Vietnamese infantry, the enemy found the M48 hard to stop. Especially at the company level, U.S. forces began to find a variety of ways to employ armor, such as avoiding heavily booby-trapped jungle paths and using the tank’s bulk to batter out their own path, instead. And once contact was made, the M48 proved a major contributor to overwhelming or at least suppressing the enemy.

“No M60s deployed to Vietnam; all those remained in Central Europe for use against the Soviets,” Cameron said. “But M48s took a lot of hits and, even if one ran over a mine, the crew was likely to survive. So it was a powerful weapons platform used in many different environments, including rubber plantations, urban areas and during the Tet offensive. The gun also could fire a canister round, which created multiple bad days for threat personnel.”

When the first Sheridans arrived in Vietnam, their light weight and maneuverability were seen as major pluses, the canister round was a highly effective defoliant and the main gun’s conventional round proved to be an excellent bunker buster. But there also were negatives: The aluminum hull was vulnerable to mines and rockets, especially if hit in the magazine; the Sheridan’s combustible cartridge sometimes left smoldering debris in the tube, creating the potential for a catastrophic accident when the loader put a new round in the tube; the North Vietnamese soon became more adept at countering armor, placing a light system in even greater danger.

One complaint against the Sheridan had little import in Vietnam – firing the main gun tended to destabilize the Shillelagh missile control system. By the time the Sheridan arrived, there was not much of an armor threat remaining in Vietnam requiring the missile. However, that problem was a serious concern for the tank’s possible use in Europe.

The military came out of Vietnam believing there were few armor lessons to be learned from the experience that could be applied to what was still considered the real probable future battlefield – Central Europe.

In the early 1970s, the U.S. and Germany began a program to replace the M60 with the MBT-70, which could operate in a nuclear-biological-chemical (NBC) contaminated environment. However, the program soon became overly expensive for the Germans, who pulled out in favor of new upgrades to their Leopard tank. Congress agreed and the program died, leaving the U.S. Army with no future MBT program and forced to follow the German path with upgrades to the M60, which originally had been intended only as a temporary platform.

In 1972, the Army convened an MBT Task Force at Fort Knox to generate requirements for a new main battle tank. Comprised of engineers, active duty military and veterans, the MBTTF looked at tank engagements from WWII through Vietnam. However, much of what they pulled from those experiences was made obsolete by the Yom Kippur War in October 1973, which proved a shock to what they thought they knew about tank warfare.

“The Arab states invaded Israel with large masses of relatively new Soviet equipment. Their attack began with no warning and they came close to inflicting a crushing defeat on Israel. They also introduced the Soviet-made Sagger anti-tank guided missile, which could be operated by an individual from a portable controller, increasing battlefield lethality overnight. The initial Israeli response was tank heavy counterattacks, which led to heavy losses, most due to Saggers,” Cameron said.

“For us, the big issue was a possibility the next war, with the Soviets, would be come-as-you-are, with no long time to organize and deploy forces overseas. For armor, there were a lot of concerns about the M60, which was our primary battle tank and first line of armored defense, because the M60 suffered a lot of casualties in Yom Kippur. So the Task Force was keenly interested in what happened in that war, which was the largest series of tank engagements since World War II. The Army invested a lot of energy in gathering data on tactics and results, which then were fed directly into the ongoing development of what became the M1A1 Abrams design.”

One almost immediate change was a new priority for crew survivability and comfort. U.S. tanks were large, to accommodate the majority of America’s physically large male population, which meant larger turrets and interior space. By contrast, Soviet tanks were much more cramped, with crew comforts few and far between. For the U.S. and NATO, a certain level of comfort was required so crews would not fatigue as quickly and could sustain days of continuous conflict. The Soviets were more interested in a quick breakthrough – application of mass at a decisive point – so crew comfort was not a high priority.

Perhaps the single biggest change in tank structure was how armor was incorporated.

“The big advance came in the change from a cast hull, which had its own problems because, when hit, even if you did not penetrate, the back side of the hull would splinter off and throw fragments into the interior,” according to Dr. Douglas Templeton, deputy associate director for ballistic protection at the Army’s Tank Automotive Research, Development & Engineering Center (TARDEC). The big change came in what evolved into the Abrams.

“As Abrams emerged into more specific concepts, Congress questioned the wisdom of a new tank design. In the late 1960s, there had been a lot of concern about the Sheridan; the Army put a significant amount of money into building those and got a platform that was never ideal. And the MBT70 added to that. So in the 1970s, Congress was skeptical about the Army’s ability to design a new tank,” Cameron said.

NEXT: Abrams Becomes a Game-Changer

Editor’s note: This article was first printed in The Year in Defense: Review Edition in an abridged version as “Armor: Three Decades of Advances.” It is now appearing online in its original form, in four parts.

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