Key point: Tank-destroyers also taught the Army not to over-specialize. There was no need for multiple classes of tanks that were strong in one respect and weak in another.

During the 1940s, the U.S. Army developed a special weapon to counter the tanks of the German Wehrmacht. Most of these vehicles had the hull of a Sherman tank and a turret with a long-barrel cannon.

But don’t dare call them tanks. These were tank-destroyers.

After the war, the U.S. Army concluded tank destroyers were a waste of time. Official histories excoriated the failure of the program.

But a look at historical records shows that tank destroyers actually did their job well.

The tank-destroyer force was the Army’s response to the wild successes of German armor in Poland and France in 1939 and 1940. Panzer divisions would concentrate more than a hundred tanks on a narrow front, overwhelming the local anti-tank weapons of defending troops and rolling deep into enemy lines.

In 1941, the Army concluded that it needed mobile anti-tank units to intercept and defeat German armored spearheads. Towed anti-tank guns took too long to deploy on the move and it was difficult to guess where the enemy would concentrate for an attack. Instead, self-propelled anti-tank battalions would wait behind friendly lines.

When the German armor inevitably broke through the infantry, the battalions would deploy en masse to ambush the advancing tank columns.

The Army didn’t intend for its own tanks to specialize in defending against enemy panzers. The new armor branch wanted to focus on the same kind of bold armored attacks the Germans were famous for.

The Army tested the concept out in war games at Louisiana in September 1941. Tank-destroyers performed extremely well against tanks — perhaps because, as the armor branch alleged, the “umpire rules” were unfairly tilted in their favor. Tanks could only take out anti-tank units by overrunning them, rather than with direct fire.

M10 and M36 Tank Destroyers 1942-53 (New Vanguard)

With the support of the Army’s chief of training and doctrine Lt. Gen. Leslie McNair, tank-destroyers became their own branch in the army, just like armor and artillery already were. A tank-destroyer center began training units at Fort Hood, Texas. Fifty-three battalions of 842 men each initially mobilized, with plans to grow the force to 220 battalions.

Each battalion had 36 tank-destroyers divided into three companies, as well as a reconnaissance company of jeeps and armored scout cars to help ferret out the disposition of enemy armor so that the battalions could move into position. The recon company also had an engineer platoon to deal with obstacles and to lay mines.

The first tank-destroyer units made do with hastily improvised vehicles. The M6 was basically an outdated 37-millimeter anti-tank gun mounted on a three-quarter-ton truck.

The M3 Gun Motor Carriage, or GMC, was an overloaded M3 halftrack — a vehicle with wheels in the front and tracks in the rear — toting a French 75-millimeter howitzer on top. Both types were lightly armored and lacked turrets.

Scooting and shooting in Tunisia

Though some M3 GMCs resisted the Japanese invasion of The Philippines, tank-destroyer battalions first saw action in the deserts of North Africa starting in 1942.

Their most important engagement pitted the M3s of the 601st Tank Destroyer Battalion against the entire 10th Panzer Division in the battle of El Guettar in Tunisia early in the morning on March 23, 1943.

Deployed in defense of the 1st Infantry Division just behind the crest of Keddab ridge, the 601’st 31 gun-laden halftracks moved forward and potted off shots at the panzers as they rolled down Highway 15, then scooted back and found new firing positions. They were bolstered only by divisional artillery and a minefield prepared by their engineers.

Two companies from the 899th Tank Destroyer Battalion reinforced them at the last minute, one of them suffering heavy losses while approaching.

The panzers advanced within 100 meters of the 601st’s position before finally withdrawing, leaving 38 wrecked tanks behind. However, the 601st had lost 21 of its M3s and the 899th lost seven of its new M10 vehicles.

The heavy losses did not endear the tank-destroyers to Allied commanders. Gen. George Patton said the tank-destroyers had proved “unsuccessful.”

In fact, the battle of El Guettar marked the only occasion in which U.S. tank-destroyers were used in the manner intended — deployed as an entire battalion to stop a German armored breakthrough concentrated on a narrow front.

The German army remained largely on the defensive in the second half of World War II, and failed to achieve armored breakthroughs like those in Poland, France and Russia. As a result, the U.S. Army scaled back the number of tank-destroyer battalions to 106. Fifty-two deployed to the European theater and 10 to the Pacific.

Another problem was that tank-destroyer doctrine presupposed moving into ambush positions after the German tanks had already overrun defending infantry. In practice, nobody wanted to consign the infantry to such a fate, so tank-destroyers deployed closer to the front line for forward defense.

The first proper tank-destroyer was the M10 Wolverine, which featured the hull of the M4 Sherman tank and a new pentagonal turret. General Motors and Ford produced 6,400 M10s.

The Wolverine mounted a long-barrel high-velocity 76-millimeter gun thought to have good armor-piercing performance. However, it had less effective high-explosive shells for use against enemy infantry — at least, compared to the 75-millimeter shells fired by Sherman tanks.

Naturally, tank-destroyer units carried more armor-piercing shells than high explosive shells, while the reverse was true in tank units.

Germany, Italy, Japan and Russia all fielded tank-destroyer vehicles, as well. Some were simply anti-tank guns mounted on a lightly-armored chassis, such as the Marder and Su-76, while others were heavily-armored monstrosities with enormous guns, such as the Jagdpanther and the JSU-152.

None had turrets. These were seen as expensive luxuries unnecessary for the defensive anti-tank role. American doctrine envisioned a more active role, thus the turrets. However, the M10’s hand-cranked turret was so slow it took 80 seconds to complete a rotation.

While Sherman tanks had three machine guns, the M10 had just one pintle-mounted .50-caliber machine gun that could only be fired if the commander exposed himself over the turret. Movie star Audie Murphy won the Medal of Honor when he repelled a German assault near Colmar, France using the machine gun of a burning Wolverine.

The M10’s biggest deficit lay in armor protection. The Wolverine had an open-top turret, meaning the crew was exposed to shrapnel and small-arms fire from above. Its armor was also thinner overall than the Sherman’s was.

These shortcomings had their rationales. Even the heavier armor on a Sherman could be reliably penetrated by the long 75-millimeter guns of the standard German Panzer IV tank, let alone the more potent guns on German Panther and Tiger tanks.

Therefore, the Wolverine’s inferior protection made little difference against those vehicles. It did leave the M10 more vulnerable than the Sherman to lighter anti-tank weapons, but these were no longer very common.

Likewise, the M10’s open top gave the crew a better chance of spotting the enemy tanks first — usually the factor determining the winner of armor engagements. It would rarely be a weakness when only fighting tanks. Of course, it would be a problem when engaging enemy infantry and artillery, but that was meant to be the Sherman’s job.

The M10 fully replaced the M3 GMC by 1943, but its superior gun proved less of a panacea than the Army had hoped. The Sherman tank’s short 75-millimeter gun was unable to penetrate the frontal armor of German Tiger and Panther tanks, which accounted for roughly half the Wehrmacht tank force by 1944.

The Wolverine’s 76-millimeter gun supposedly could — but experience in combat showed it failed to penetrate the frontal armor of Germany heavy tanks at ranges greater than 400 meters. A problem known as shatter-gap meant that the tip of the 76-millimeter shell deformed when it hit face-hardened armor plate at long distances, causing it to explode before penetrating.

The tank-destroyer’s inability to take out the best enemy tanks heightened the branch’s generally negative reputation.

In the Italian campaign that began in 1943, German armor was rarely encountered in large numbers, and M10s were often asked to provide fire support for the infantry. They were even used as indirect-fire artillery. Though firing lighter shells, a tank-destroyer battalion had twice as many gun tubes as 105-millimeter artillery battalion did, and longer range.

Instead of holding tank-destroyers in corps reserve, it became standard practice for commanders to attach a tank-destroyer battalion to front-line infantry divisions. Rather than fighting as unified battalions, companies or platoons of tank-destroyers would detach to provide direct support to infantry and combined arms task forces. For every anti-tank round the tank-destroyers fired, they fired 11 high-explosive rounds.

Doctrinaire officers complained that the M10s, vehicles in most respects similar to a tank, were being employed as if they were tanks. Gen. Omar Bradley suggested that the Army should instead use heavy towed anti-tank guns, which could be more effectively concealed in dense terrain.