How to kill a Panzer

The evolution of American tank destroyers

U.S. tank destroyers. Left to right: M3, M10, M18, M36
(Photo: U.S. Army)

World War II was the crèche of many types of weapons we still have today. While tanks, fighters and bombers had already been invented in World War I, the second global conflict played a vital role in helping them find their military niches. Other weapons, such as assault rifles and jet fighters, were first created in World War II. Today’s article, however, is about one particular type of weapon that, while making a distinctive appearance in World War II, did not survive the war – at least not without some major changes. Self-propelled tank destroyers were the product of a very specific time, and the end of the war forced them to evolve into something quite different.

M10 tank destroyers in Belgium during World War II
(Photo: U.S. Army)

37 mm guns were generally sufficient to take out tanks in the decades between the two World Wars, but this situation was rapidly changing with the appearance of newer, better-armored tanks in the late 30s. Better tanks could only be destroyed by larger, heavier guns – but these would be much harder to move around, especially in the new, high-speed maneuver warfare that was looming on the horizon.

An M6 “Fargo” gun motor carrier, one of the U.S.’s less successful tank destroyer designs, with a 37 mm gun (on the right)
(Photo: U.S. Army)

Germany’s invasion of Poland in September 1939, then France in May 1940, showcased this new type of warfare and made American military planners sit up and take notice. Military wisdom received from World War I held that tanks should be dispersed evenly among infantry as they attack on a wide front. Consequently, anti-tank guns should also be dispersed in a similar way so they could stop enemy tanks along the entire front. The new German Bewegungsrkieg (“mobile war,” better known by its unofficial nickname Blitzkrieg) doctrine broke with this tradition. It grouped tanks into a concentrated “spearhead” assisted by mechanized infantry and aircraft, and attack a single narrow area of the defender’s lines to create a breakthrough. Dispersing one’s anti-tank guns suddenly no longer made sense, since the few guns in the section under attack would be overwhelmed by the number of enemy tanks.

A column of German tanks and mechanized infantry advancing during the invasion of the Soviet Union
(Photo: Bundesarchiv)
American doctrine held that the primary purpose of tanks should be to support infantry in breaking through enemy lines. Therefore, enemy tanks had to be engaged by different weapons, since every tank used for tank hunting meant one less tank that could be used for its “true” purpose.
 
Two main American lines of thought emerged in response. Lesley McNair (Read our earlier article – The Army’s architect) initially wanted to use towed anti-tank guns. These were small and easily camouflaged to make a very difficult target, and cheap enough to produce in large numbers. Another idea, however, was being pushed by Lieutenant Colonel Andrew Davis Bruce, head of the Anti-Tank Planning Board. A World War I veteran with an aggressive approach to fighting, he wanted anti-tanks to be mounted on fast vehicles. His idea was to keep this “tank destroyers” in reserve behind the front line until an enemy attack. Once the enemy committed their armored spearhead to a specific location, infantry on site would hold them up as long as they could, while these vehicles would rapidly move into the area and take up camouflaged and dug-in positions along the path of the enemy attack. Once the enemy broke through, they would drive straight into the middle of an ambush.
1954 photo of Andrew D. Bruce, one of the pioneers of U.S. tank destroyer development
(Photo: University of Houston)

These tank-destroyers had to be fast so they could reach the threatened area from their reserve location in time. In order to be fast, they had to be light. They couldn’t skimp on the size and weight of their gun, which had to be able to punch through enemy tanks, so they had to save weight on armor, making them relatively defenseless. The speed would be used tactically: once the incoming enemy tankers figured out where the ambushing vehicles were and started returning fire, the destroyers would rapidly withdraw to set up a new ambush further back.
 
The support of Army Chief of Staff General George C. Marshall ensured that Bruce’s vision of a fast, reactive self-propelled tank destroyer force won out, though McNair’s idea of towed guns was not fully discarded, either. All that remained was to develop the actual tank destroyer.

An M10 tank destroyer camouflaged next to a haystack
(Photo: U.S. Army)

The U.S. Army experimented with mounting a variety of guns on a variety of vehicle chassis over the course of the war, with most attempts never making it past the prototype stage. The earliest attempts involved 37 mm guns placed on various jeeps (Read our earlier article – The Jeep), small trucks and armored cars – all of them failed, essentially because an overly large and heavy gun was put on an overly small vehicle. (Additionally, as mentioned earlier, 37 mm guns were rapidly becoming obsolete.) The one design that got closest to success was the M6 “Fargo” Gun Motor Carriage, a light truck carrying a 37 mm gun. It was undergunned and unarmored, and the only reason why 5,300 of it was produced was that it was available early on.

An M6 Fargo
(Photo: U.S. Army)
The first design that was not a clear failure was M3 Gun Motor Carriage. (It should be noted that “Gun Motor Carriage,” “GMC,” was the U.S. Army’s catchall term for all self-propelled artillery pieces, not just anti-tank guns.) The M3 was a 75 mm M1897 gun mounted on an M3 half-track. (Read our earlier article – The American half-track) The M3 GMC was always intended to be a stopgap measure until a proper tank-destroyer could be developed. Nevertheless, a force of M3 GMCs from the 602st Tank Destroyer Battalion hold the distinction of fighting in the only battle of the war where tank destroyers were used exactly the way they were envisioned.
Two M3 GMCs in British use in Italy
(Photo: Imperial War Museums)
In the Battle of El Guettar in Tunisia in late March-early April 1943, a force of 31 such half-tracks, 5 lighter tank destroyers with 37 mm guns, and 10 newer M10s fought an advancing German force of 57 tanks, Panzer IVs (Read our earlier article – The German workhorse: Panzer IV) led by Tigers. The American force managed to destroy 30 to 52 of the German tanks. (Sources disagree on the exact number.) The defenders lost 27 of their M3s and 5 of the M10s, but since a tank destroyer cost much less than a proper tank, this was still a clear American victory in terms of material loss.
 
Further experiment to make a new tank destroyer involved a 57 mm gun, the British QF (Quick Firing) 6-pounder. British and Soviet experts liked some of the resulting vehicles, but the Americans considered these a failure: the 6-pounder’s APC (“Armor-piercing, capped”) shell was still under development, and it looked like it would turn out to have worse penetration at ranges over 500 yards than the older 75 mm gun mounted on the M3. The 57 mm gun was thus rejected for use on American tank destroyers, but still saw use by U.S. infantry as a towed weapon.
The T48, a design using the 57 mm gun created for British use. The majority of these ended up in Soviet hands as Lend-Lease.
(Photo: tankarchives.ca)
The next big step after the M3 GMC was the M10, the first “tank-like” American tank destroyer with tracks and a turret. The vehicle was sometimes referred to as Wolverine, but this nickname was only used in wartime advertising and was not used by actual troops. The M10 was a modified M4 Sherman (Read our earlier article – The M4 Sherman) chassis with a thin, light turret on top mounting a 3-inch M7 anti-aircraft gun adapted for anti-tank use. True to the design principle of high speed, heavy weaponry and light armor, the turret’s armor was incapable of withstanding anything heavier than small arms fire. In fact, it didn’t even have a roof; the crew was exposed to mortar and artillery fire, air bursts, grenades lobbed into the turret by enemy infantry, and small arms shooting down at them from upstairs windows (not to mention rain). Beyond making the vehicle lighter, other upsides of the open turret were better vision for the crew and more space to facilitate rapid reloading.
The M10 GMC
(Photo: Library of Congress)
The turret was an unusual design choice. Some early German tank destroyers had their gun on top of a vehicle, but they could not rotate, forcing the destroyer to aim with its entire body. Later German designs, as well as Soviet ones, preferred the gun to be located inside the chassis rather than on top. This still meant the vehicle had to turn toward the enemy, but it also made the destroyer lower, and therefore easier to camouflage or dig in; it also allowed the chassis to be given thicker armor without compromising too much on weight and speed. The M10 and subsequent American designs sacrificed these advantages in favor of being able to turn the gun independently of the chassis, allowing the crew to engage enemies in any direction.
 
The M10 was the first tank destroyer of this general design and had its share of teething problems. The gun’s barrel was so heavy that if the vehicle was on a slope of more than four degrees, the crew found it impossible to traverse the already slow hand-cranked turret upslope; this fault had to be fixed by adding counterweights to the turret to make it less front-heavy. Beside the gun, the M10 was also equipped with a single .50 caliber Browning machine gun (Read our earlier article – The Browning .50 cal) against enemy infantry and aircraft, which was far lighter firepower than what the Sherman enjoyed thanks to its multiple machine guns.
An M10 on a mountain road overlooking a valley in Italy. The photo showcases the type of terrain where the high speed of tank destroyers was not much use.
(Photo: Library of Congress)
The M10’s engine also left something to be desired: its top road speed of 25-30 mph (40-48 km/h) was not particularly fast despite being built for a doctrine that emphasized speed. Additionally, it did not have an auxiliary generator, which meant that the vehicle’s batteries could only be recharged while the engines were running. This, in turn, created noise and smoke which made it easier for the Germans to spot the tank destroyer.
 
Despite its shortcomings, the M10 became the most-produced American tank destroyer of the war with over 6,400 built. It first fought in North Africa in March 1943, where Its 3-inch gun was adequate against German tanks during the African campaign but would later prove unable to penetrate the front armor of the new Panther tanks.
An M10 on display at the Overlord Museum in Normandy
(Photo: Author’s own)
The next iteration was the M18 Hellcat, which doubled down on the “fast but lightly armored” design. Rather than built on the heavy Sherman chassis, the Hellcat had its own chassis designed for speed, and could, indeed, reach an impressive 55 miles per hour (88 km/h) on roads, with an offroad speed of 26 mph (41 km/h). The tradeoff, of course, was even less armor than on the M10, with armor thickness generally half of its predecessor. The design retained the roofless, thin turret, but mounted a better weapon: the 76 mm gun M1, the same gun that would later be installed in newer models of the Sherman. One quirk of the Hellcat was that its long gun barrel, muzzle brake and large roadwheels made it look a bit like a German tank from a distance, which made crews wary of friendly fire incidents.
An M18 Hellcat. Note how the chassis is distinctly different from the M10’s.
(Photo: U.S. Army)
The Hellcat first saw action in Italy in the spring of 1944, when several prototypes were used in the breakout from the Anzio beachhead. (Read our earlier article – Anzio: “a vain-glorious blunder”) The improved firepower was a welcome change, but its superior speed could rarely be used to full advantage in the enclosed, mountainous terrain. Still, when it did get into combat with German tanks, the M18 was capable of moving too fast for German turrets to keep up with, allowing it to attack the flanks of the enemy.
 
Additionally, the nature of the war had changed by 1944. Germany was no longer on the offensive, and could not mount the large, massed armored attacks that U.S tank destroyers were designed to blunt. The tank destroyers, which were originally grouped into battalions and held in reserve, were broken up into smaller units and assigned to provide supporting fire to infantry forces, essentially acting as poorly armored tanks.
An M18 firing its gun in Germany
(Photo: U.S. Army Signal Corps)
Putting tank destroyers into an infantry support role was necessary, since there was no longer a need for them in their original roles, and it would have made no sense not to use them for anything. This change did, however, came back to haunt the U.S. Army in the winter of 1944-45, during the Battle of the Bulge. Germany’s final major push on the Western Front was one final battle where battalion-sized tank destroyer formations rushing forward to stop an armored attack would have been extremely useful. As it happened, there was no time to recall the vehicles from their infantry units and reconstitute such battalions.
An M36 used in an indirect fire role to support infantry
(Photo: U.S. Army)
The final iteration of the American tank destroyer in World War II was the M36, sometimes called by its unofficial post-war nickname Jackson. The M36 was designed to replace the M10 and was inspired by the success of the German 88 mm flak cannon, which also proved to be a terrifying weapon against infantry and armored vehicles. The equivalent American weapon was the 90 mm M1, which was mounted, once again, on a Sherman chassis. It featured much-improved frontal armor, though this came at the cost of speed, and the M36 was actually a bit slower than the M10.
An M36 during the Battle of the Bulge, with a canvas pulled over the roofless turret for minimal protection against the cold
(Photo: U.S. Army Center of Military History)
Nevertheless, the excellent firepower combined with decent protection made the M36 a formidable weapon against all German tanks, even though its shots could still be stopped by some parts of the Panther’s frontal armor, and the Tiger II could still only be damaged in a few weak spots. The M36 was well-liked by its crew and went on to serve in Korea and later wars. In fact, two M36s were in service in Taiwan until 2001.
1958 photo of an M36 in Yugoslav service being carried by a truck
(Photo: Jože Gal)
Despite the long service of the M36, the sun rapidly set over the tank destroyer as imagined by the United States. The idea of using a vehicle only for killing tanks and nothing else had already eroded during World War II. Additionally, stronger engines gave rise to the main battle tank that combined heavy firepower, thick armor and high speed, making it unnecessary to sacrifice one of the three qualities for the other two.
 
Nevertheless, the idea of taking out a tank with a smaller and cheaper vehicle persisted into the Cold War and the present day. The development of anti-tank missiles such as the TOW (“Tube-launched, Optically tracked, Wire-guided”) made it possible to easily equip a wide range of vehicles with anti-tank capabilities. Many such vehicles serve in the armies of the world today, and while they are no longer called “tank destroyers,” they nevertheless follow the same basic idea that arose out of need before World War II. 
An ATGM carrier based on the Swiss Mowag Piranha family of armored fighting vehicles, one of the many “spiritual successors” of World War II tank destroyers
(Photo: Sandstein / Wikipedia)

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A paratrooper landing at Mont Saint-Michel, France to honor paratroopers who descended on D-Day
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