There has been intense discussion during the past few months of whether, when, and how the U.S. might provide its most advanced tanks to Ukraine. Although they might not be as sexy as F-22 fighter planes or hypersonic missiles, like the offensive linemen in football, they can alter the course of the game.
Tanks originated during World War I as a means to break the stalemate of trench warfare. The opposing forces had bogged down behind long trench lines facing each other that extended from the North Sea to the Alps. Between the trenches was no-man’s land, an area hundreds of yards wide. Because of the advent of the machine gun and rapid-fire artillery, it was nearly impossible to cross no-man’s land on foot. Mass attacks resulted in enormous casualties; the Allies suffered nearly 60,000 casualties in a single day at the Battle of the Somme. Something was needed to break the stalemate. It had to be something mobile that could provide protection against machine guns and artillery shell fragments as well as traverse barbed wire barricades and, if possible, span trenches.
In short, what was needed is what we now think of as a tank. Many designs were tried and early designs were not fully successful, but by spring 1918, effective designs had evolved that allowed the Allied Powers to break through the German trenches go on the offense. Some of these tanks, such as the British Mark IV shown here, looked quite different from those today, but they provided the necessary combination of mobility, firepower, and protection. And they worked. Germany’s lines were breached, its armies defeated, and an armistice signed in November 1918.
In the years after World War I, many nations made rapid advances in tank design and technology. Mobility was greatly increased from the roughly 4 mph of the Mark IV to 25 mph for the German Panzer 4. Turreted designs were commonly adopted and the main gun was increased from machine-gun type weapons to 50mm and eventually 88mm cannons.
Because of the larger guns, armor thickness had to be increased up to as much as 80 millimeters. Progress in many nations was roughly equal, and at the outset of World War II, German tanks were not regarded as superior to those of other nations. However, the Germans had introduced two significant innovations. First was the inclusion of a radio in most tanks. This allowed far better coordination of actions. Second was the combined-arms Blitzkrieg, which had tanks, aircraft, artillery, and infantry operating in a coordinated and extremely aggressive manner. In the early days of the war, these operations often overwhelmed defenses before they had a chance to set up. And unexpected tactics such as bypassing the French Maginot line by going through the supposedly impassible Ardennes Forest resulted in the rapid defeat of Belgium, the Netherlands, and France in 1940. Once the war was well underway these tactics were less effective. Nevertheless, the decisive role that effective tank warfare could play was well established.
During WW II, the M4 Sherman tank with its 75mm gun was the U.S. workhorse. In total, nearly 50,000 were produced. The Soviet forces used primarily the T34 with its 76mm gun and later with an 85mm gun. Nearly 80,000 of these were built. Although this was a very effective tank, toward the end of the war Soviet Union introduced the T54/T55 series with a 100mm gun. This tank was expected to dominate any tank battle and eventually about 100,000 were produced. This is the most prolifically produced type of tank in history.
To counter this, in 1952 the U.S. introduced the M48 Patton tank, originally outfitted with a 90mm gun. Although this was an effective tank, it was already outgunned by the T-54/T-55 tanks, so in 1959 the U.S. introduced the M60 tank with a 105mm gun. Its superiority was short lived however. Soviet tank designers had a saying, “use plenty of gun,” and in 1961 they introduced the T-62 with a 115mm gun. This was about as large a projectile as could be loaded by a human, but the Soviet designers were not overly concerned with ergonomics and comfort; the joke was that to be a T-62 ammunition loader you had to be a left-handed midget weightlifter. Evidently, such people were not in short supply as the USSR eventually fielded nearly 23,000 of these. U.S. production of the M60 totaled about 15,000.
But the U.S. was about to fall further behind in the tank race. In 1972, the Soviets began production of the T-72 with a 125mm gun. This gun required an autoloader so the crew was reduced to three people. These guns were capable of firing long-rod kinetic energy penetrators made of tungsten, which were more accurate than other rounds and could easily penetrate the armor of the M60. Long-rod kinetic energy penetrators are essentially just heavy, dense arrows that are fired at very high velocities and rely on their momentum and energy to penetrate a target. Because the rods themselves are much smaller diameter than the gun caliber, they require a sabot to keep them centered in the gun tube and allow the propellant to push them forward. The sabot consists of two or three sections so that it separates from the long-rod as soon as it leaves the muzzle of the gun, and only the long-rod flies forward to the target. The long-rod shown below is close to three feet long and weighs about 10 pounds.
The M1 Tank
By the 1970s, the U.S. badly needed an improved tank that could counter the USSR’s T-72. But in the aftermath of Vietnam, funds for new weapons were sparse, so to justify design and production costs, any new tank needed to be a significant improvement over the M60. Various designs were advanced such as the MBT-70/XM803, which put all four crew members into the turret in order to reduce the overall vehicle height, but it succeeded mostly in making the driver nauseous. In any case, it would have been inferior to the T-72.
Fortunately, several innovations came together in the 1970s that resulted in a vast improvement in capabilities for the M1 tank. The first of these was the development of so-called “Chobham armor” or its more generic version, “special armor.” Up to that point, tank armor was effective against bullets, artillery shrapnel, and (hopefully) rounds fired by other tanks. But nearly all designs were vulnerable to even relatively small shoulder-launched shaped charge weapons, not to mention larger anti-tank missiles. The shaped charge is truly a wonder of nature: it consists of a thin copper cone backed by explosive. When detonated, the copper forms a jet that can penetrate steel, making a hole that is several times the diameter of the charge in depth.
Tank designers had pretty much given up on protecting against shaped charges, but that changed with the advent of “special armor.” Its precise composition is still secret, but it consists of an array of spaced plates of various compositions that break up and disperse the stream of the shaped charge jet. This is called non-explosive reactive armor, or NERA. The M1 incorporated this into its design and it protected against most of the hand-held infantry weapons and, in the frontal sector, even against many of the larger anti-tank missiles.
The second innovation was the incorporation of a separate ammunition compartment with blow-out panels. In other tanks, ammunition detonations are the deadliest thing that can happen. In the M1, most of the tank ammunition is stored in the rear of the turret in a specially constructed bustle that incorporates automated sliding doors facing the crew and blowout panels on the top. In the event that the ammunition is struck by a shaped charge jet it will usually detonate, but the blast will be diverted through the blowout panels and will not enter the crew compartment.
The third innovation was the development of depleted uranium (DU) as an exceptionally dense, high-strength material. There was a large supply of raw material in the form of spent fuel from nuclear reactors, but its basic properties were not appropriate. However, intensive efforts in metallurgy resulted in a very high-strength, tough material with a density of 19 grams per cubic centimeter, more than two-and-a-half times the density of steel, and even higher than high-strength tungsten alloys. This seemed to solve two problems simultaneously: provision of an excellent material for long-rod penetrators and armor, and a reduction in the amount of depleted uranium at reactor sites. Therefore, in the U.S., DU became the material of choice for long-rod penetrators. Initially it was used to make an improved 105mm long-rod penetrator in order to keep the 105mm tank gun relevant. As a result, the first M1 tanks were outfitted with 105mm guns.
However, as the ramifications of the Russian 125mm guns became more widely appreciated, two things became apparent. First, a bigger gun was needed. Fortunately, the Germans had developed a 120mm gun that was tested at Aberdeen Proving Grounds and found to be quite capable. The muzzle velocity of rounds fired from this gun can exceed a mile per second. As a result, the M1A1 and subsequent variants were fitted with the 120mm gun. This gun proved its worth during Operation Desert Storm when kills of opposing tanks were recorded at ranges of nearly four kilometers.
Also, to address the Russian long-rods, DU panels were added to the armor. This has proved successful in combat. During Desert Storm, the M1A1 frontal armor protected the crew from projectiles fired by Iraqi tanks and even other M1A1s in friendly fire incidents.
Two other innovations were the incorporation of a 1,500-horsepower multi-fuel turbine engine, which provides a very high horsepower-to-weight ratio and allows the M1 to achieve road speeds of 45 miles per hour, and the installation of an excellent gun-stabilization system that allows the M1 to hit another tank at more than two kilometers range (about a mile and a quarter) while moving.
Additional improvements, mostly electronic, were made in the M1A2, which included things such as GPS navigation, digital maps, situation awareness displays, and improved night vision devices. Beyond that, several improvements and add-on kits have been developed, most notably the Tank Urban Survival Kit (TUSK) that added reactive armor tiles to vulnerable spots, and the Trophy Active Protection System (APS) that can shoot down anti-tank missiles before they hit.
Will The M1s Make A Difference In Ukraine?
The short answer is no, for several reasons. The U.S. has pledged 31 M1 tanks but they will not arrive for at least a year. We will not send tanks with DU armor because the composition is still secret and because of the difficulty of cleanup if the armor is breached, so they will have to be re-manufactured with alternate armor or taken from stocks of other export versions. In any case, 31 tanks is a pittance in a war that has already seen roughly a thousand Russian tanks destroyed.
In support of the government’s fight against ISIS, we gave more than 300 M1s to Iraq, so 31 is largely symbolic; their real purpose is to induce the Germans to provide 100 or more of their tanks during 2023. It is possible that those tanks will arrive in time and in sufficient numbers to make a difference, but even that number will have to be used very strategically if they are to have a significant impact. Russia has a huge advantage in numbers of tanks, so frontal assaults on Russian tank positions would quickly deplete the limited Ukrainian supply. Instead, their high mobility must be used to stage hit-and-run ambushes and Blitzkrieg-style rear-area raids.
Unfortunately, despite our advances in armor protection, greater advances in anti-tank missiles have been developed, as exemplified by our own Javelin, which has devastated so many Russian tanks. Russia also has plenty of effective anti-tank missiles, which are widely deployed and hard to detect. A solution would be to provide the Ukrainians with tanks outfitted with the Trophy active protection system, which has radar that can detect incoming missiles and rockets and shoot them before they hit the tank. Trophy is a game-changer that largely eliminates the threat from anti-tank missiles and would allow much more flexible use of the tanks. The U.S. has outfitted several hundred M1s with Trophy; unfortunately, this does not appear to be in the cards for Ukraine.
There is hope, however. Ukraine has shown great resourcefulness in its execution of the war thus far, and we expect that they will use these new assets wisely.
Tom Hafer developed systems for neutralizing rockets and drones. He currently coaches teenage robotics teams. Henry I. Miller, a physician and molecular biologist, was a research associate at the NIH and the founding director of the FDA’s Office of Biotechnology. They were undergraduates together at MIT.