When the Panzer-led German Blitzkrieg sliced through Polish and then French forces, the US Army realized it needed better anti-tank weapons and tactics, so it produced a tank destroyer force — a new combat arm within the Army’s ground forces, coequal with infantry, artillery, and armor — with its own manual — Field Manual (FM) 18–5, Tank Destroyer Field Manual: Organization and Tactics of Tank Destroyer Units:
Encouraged by Marshall and McNair, Bruce infused the doctrine with an aggressive, offensive spirit, as characterized by the term tank destroyer and by the motto “Seek, Strike, and Destroy.” The hallmarks of this doctrine were mobility and firepower. Assuming that the main threat would be masses of light tanks operating at top speed, FM 18–5 posited that tank destroyers would use superior mobility to hem in the marauding tanks, maneuver against their flanks, and employ superior firepower to destroy them. In Bruce’s mind, tank destroyer operations assumed the character of the counterattack rather than passive defense.
That’s not quite how things played out in North Africa:
It came as something of a shock when panzer divisions behaved differently than the enemy described in FM 18–5. Rather than masses of light tanks operating at top speed, the panzer divisions in Tunisia employed sophisticated combined arms teams, characterized by artillery and infantry operating in close support of the tanks, and deadly antitank fire coming from hidden overwatch positions. For the lightly armored tank destroyers, slugging it out with German tanks in the open was suicidal. It quickly emerged that the best way to meet attacking German tanks was from concealed dug-in positions — a far cry from Seek, Strike, and Destroy. This fact also doomed the idea of tank destroyers being held back in reserve, to race fire-brigade style to the scene of a German attack. If the antitank units were not on hand when the attack began, they would have to join the battle in progress and possibly have to fight exposed from a position of weakness. In any case, they were unlikely to arrive in time to retrieve the situation given the tempo of combat embodied in blitzkrieg.
Equally important, tank destroyers in North Africa operated under a handicap in regard to their equipment. Expedient weapons intended solely for training ended up fighting real panzers. The M3 Gun Motor Carriage, a 75-mm. gun mounted on a halftrack, had neither superior mobility nor firepower when confronting Axis armor. The M6, an obsolete 37-mm. antitank gun mounted on a ¾-ton truck, was hopeless. The best expedient was the M10, a 3-inch gun mounted in a fully rotating open-topped turret on the chassis of an M4 Sherman tank.
Finally, the tank destroyers in North Africa discovered that the rest of the Army was largely ignorant of their doctrine, if not downright hostile to the concept they embodied.
Every innovation is a gamble.
(Hat tip to Jonathan Jeckell.)