Mensaje
por José Luis » Vie Mar 05, 2010 11:15 am
¡Hola a todos!
Intervengo nuevamente en este hilo para traer la opinión muy autorizada de un oficial, Belton Y. Cooper, que sirvió en el Batallón de Mantenimiento de la 3ª División Acorazada, y que recogió sus experiencias en el libro Death Traps: The Survival of an American Armored Division in World War II (1998). Cuando digo que su opinión es muy autorizada, estoy significando que estamos ante un auténtico experto en blindaje estadounidense. Cooper se formó en la escuela de la fuerza acorazada de Fort Knox, donde adquirió el conocimiento práctico en el mantenimiento de tanques y vehículos, al tiempo de formarse en las tácticas de la guerra acorazada. Una vez entró en combate con la 3ª DA, con la preparación de los informes diarios de pérdidas, Cooper se familiarizó íntimamente con las debilidades y fallos del Sherman M4.
En el prefacio de su libro, Cooper hace unas valoraciones generales de lo que fue esencialmente una guerra de movimiento en la campaña occidental de Europa en 1944-45 y dice:
[Nuestra mayor arma para esta guerra blindada fue el MBT Sherman M4. En todas las capacidades clave de un MBT -potencia de fuego, blindaje y movilidad- el Sherman M4 fue decididamente inferior a los superiores tanques alemanes que encontró en batalla. Esta importante desventaja no sólo causó dolor, sufrimiento y pérdidas tremendas en personal y blindaje, sino que también retrasó la conclusión exitosa de la guerra en Europa].
[Our major weapon for this armored warfare was the M4 Sherman main battle tank. In all the key capabilities of a main battle tank—firepower, armor and mobility—the M4 Sherman was decidedly inferior to the superior German tanks it encountered in battle. This major disadvantage not only resulted in tremendous pain and suffering and losses in personnel and armor, but also delayed the successful conclusion of the War in Europe.] (p. 4).
En un apartado que titula “Tragic Inferiority of the M4 Sherman Tank”, Cooper dice que a menudo, cuando un impacto penetraba el blindaje del Sherman, la lluvia de fragmentos cortaba los cables eléctricos, y aunque los cables estaban protegidos con fundas blindadas, los fragmentos podían causar un cortocircuito e incendiar el tanque, cuyo destino final dependía del comportamiento de la tripulación:
[Often when a tank was penetrated, the shower of fragments would sever the electrical cables. Even though the cables were protected by armored covers, the fragments would cause a short and could set the tank on fire. If the tank crew pulled the fire extinguisher switch before evacuating, the fire would be snuffed out and the interior of the tank would burn only partially. If the crew was unable to do this, the tank would burn up completely, and the tremendous heat would soften the armor and make the tank impossible to repair.] (p. 22).
Luego continúa diciendo:
[A pesar de los defectos del M4, se nos dijo que era un buen tanque, comparable a los tanques alemanes que encontraríamos en la Europa septentrional......El Mark-IV (la terminología aliada para referirse al PzKw-IV) original tenía un cañón corto similar al 75mm M2 de nuestros M4; su velocidad de boca era de 1.500 pies por segundo. Estos habían sido reemplazados en el PzKw-IV por un 75mm KwK41 con una velocidad de boca mucho más alta (3.000 pies por segundo). El Mark-IV era un tanque más pequeño y de perfil bajo que pesaba solamente veintidós toneladas comparadas con las treinta y siete toneladas y media de nuestro M4. Tenía cuatro pulgadas de blindaje en la parte vertical frontal (glacis plate) y una oruga más ancha que el M4, que lo facultaba para sortear el terreno blando más fácilmente de lo que podía el M4]
[In spite of the flaws of the M4, we were told that it was a good tank, comparable to the German tanks we would be meeting in northern Europe. Back in the States and also in England, we had received numerous ordnance evaluation reports on German equipment, most dealing with the German PzKw IV, which we usually called the Mark IV The original Mark IV had a short-barreled gun similar to the 75mm M2 on our M4s; its muzzle velocity was fifteen hundred feet per second. These had been replaced on the PzKw IV by a 75mm KwK41 gun with a much higher muzzle velocity (three thousand feet per second). The Mark IV was a smaller, low-profile tank that weighed only twenty-two tons compared to our M4's thirty-seven and a half tons. It had four inches of armor on the vertical part of its glacis plate and a wider track than the M4, which enabled it to negotiate soft ground more easily than the M4 could.] (p. 23).
El asunto de las orugas lo detalla más adelante. Os copio en su original sin traducir para quienes tengan interés especial:
In spite of the American tanks' inferior guns and armor compared to German tanks, they were faster and more mobile on paved highways. Tracks of American tanks lasted longer and achieved greater highway speeds than those on German tanks. The key was in the design of the track block itself. The track would arc upward when it went over the final drive sprocket and would conform to the sprocket contour. As the track went down to the first bogey wheel, it was straightened out, and the tank bogeys rolled along the track. When the track reached the last bogey, the torsional energy stored in the rubber doughnuts within the track caused the track to pick itself up slightly and thus go over the rear outer sprocket more easily.
This made the entire track an energy accumulator. Part of the energy put into the track as it bent around the final drive sprocket was recovered when the track returned over the rear-idler sprocket. Thus, the tank could move with less horsepower, leaving more power available for speed and mobility. In addition, the rubber covering on the track shielded the tank from road shock. This, along with the rubber-tired bogey wheels, gave the track a much longer useful life. The rubber coating on the inside of the track allowed it to be turned over and reversed after the outside had been sufficiently worn. A set of tracks for an M4 medium tank would last for approximately 2,500 miles on the highway, including one reversal. This was far superior to the German tracks, which were thought to last about 500 miles per set, after which the metal pins on the track began to break excessively.
The only problem with the American track was that it was too narrow and got stuck in muddy terrain. German tanks were designed with much wider tracks that could operate over rough, muddy ground. Because most major tank engagements took place off the road, the overall effect favored the Germans. (p. 60).
Finalmente, también os voy a copiar en su original el apéndice 1, titulado Panzer Versus American Armor, para quien tenga interés:
The M4 Sherman that we took into Normandy weighed thirty-two tons and had two and a half inches of armor, inclined at forty-five degrees, on its front glacis plate. It had a short-barreled, low-velocity (2,050 feet per second) 75mm gun. Later, about 15 percent of the tanks we received had the new 76mm gun with a higher muzzle velocity (2,650 feet per second).
When the war began in Europe, a confused debate was raging between American tank designers in ordnance and senior officers in the army ground forces. In the summer of 1939, when I was at Aberdeen Proving Ground as an ordnance cadet, our main battle tank was the M2A1 medium tank with a 37mm gun mounted in the turret. After the Germans invaded Poland in September, the debate became more intense. The armored and cavalry officers favored a large-caliber, high-velocity antitank gun mounted in the turret. The infantry officers still thought of the tank as an infantry assault weapon. The artillery officers thought that if a tank was going to carry a gun larger than a 37mm, the gun should conform to artillery specifications, which required a gun to be capable of 7,500 service rounds in combat. To meet this, a 75mm gun and larger would require a relatively low velocity. It apparently never occurred to the artillery officers that few tanks would ever survive in combat long enough to fire 7,500 service rounds. The result of this was the new M3 battle tank, designed by a committee.
This committee chose the new tank's basic features. It had the M2A1 lower hull and track system, powered by the R975C1 400-horsepower radial engine, and a transmission and final drive similar to that of the old M2A1. The side and frontal armor were increased, and an angular-shaped hull was devised using riveted connections. The front glacis plate, approximately two and a half inches thick, started out at forty-five degrees where it connected with the transmission and extended about halfway up the front. It then had a knuckle riveted joint in the middle and extended upward at about sixty degrees. The riveted joint was used because some officers felt that the welding would weaken the armor plate. This decision was disastrous. When a small-caliber, armor-piercing bullet struck the head of one of these rivets, it sheared it off and drove the internal part of it into the tank, where it ricocheted like a projectile and killed the crew.
The committee decided to put a 37mm antitank gun in the turret, coaxial with a .30-caliber machine gun. The 37mm was already obsolete and had practically no effect on the frontal armor of German tanks. The turret also had a .50-caliber ring mount, dual-purpose machine gun. The main armament, conforming to the artillery board's specifications, was a low-velocity 75mm M2 gun mounted in a barbette enclosure on the right side of the tank. With approximately forty-five degrees of lateral traverse and its low muzzle velocity (2,050 feet per second), it seemed to satisfy the infantry board as a good assault tank.
The tank had a much higher silhouette than any comparable German tank and could be easily spotted from a considerable distance. To make matters worse, the committee was apparently dominated by Yankees, who decided to name this tank the "Grant," after the Union general and later president. The Southerners were aggravated further by the later naming of the M4, known as the "Sherman," after the Union general who burned a path through Georgia.
Opposing us were three types of German panzers. The PzKw IV, which we usually called the Mark IV, weighed twenty-three tons and had four inches of vertical armor on the front and a high-velocity (3,000 feet per second) 75mm gun. Next came the PzKw V Panther, weighing fifty-three tons with three and a half inches of armor on the front glacis plate at thirty-eight degrees, below the critical angle of ricochet. The Panther carried a long-barreled, high-velocity (3,300 feet per second) 75mm gun. Finally came the PzKw VI King Tiger, weighing sixty-four tons with six inches of armor at forty-five degrees on the glacis plate and a long-barreled, high-velocity (3,250 feet per second) 88mm gun. The German tanks had a qualitative superiority of as much as five to one over our M4 Sherman.
The combination of superior firepower and heavier armor allowed the German tanks to engage and destroy the M4 Sherman at long range. There were many cases where Shermans would score multiple direct hits on the front of a Panther or a Tiger, only to see the shells bounce off harmlessly. In comparison, the German high-velocity guns could not only penetrate the lighter armor of the Sherman with a single shot at long range, they could knock out a Sherman even after shooting through a brick wall and, in at least one instance, by shooting through another Sherman tank:. Whereas the Sherman had to get within six hundred yards of a Panther and hope to catch it on the flank, the Panther could knock out a Sherman at two thousand yards head-on.
Before the Normandy invasion, some U.S. armored commanders assumed that because the Sherman was lighter than the Panther, it would be more mobile. This assumption was incorrect. The key to a tank's off-road mobility is its ground bearing pressure: how the weight of the tank is distributed over the ground. Because the Panther had a wider track than the Sherman, it actually had a lower ground bearing pressure and could go places where the Sherman could not. More importantly, the narrow track on the Sherman could not negotiate muddy terrain and snow.
The M4 Sherman's inferiority was by no means predestined; we enjoyed a great superiority in other weapons systems. After a twenty-year period of isolationism between the wars, in just four years the United States was able to produce superior weapons in vast quantities, including rifles, artillery, motor transports, and aircraft.
As the only officer in the maintenance battalion who had been to the tank maintenance school in Fort Knox, I was knowledgeable about tanks, particularly their technical capabilities. At tank school, I took copious notes and read every field manual I could get my hands on. I also read any G2 ordnance reports we had on German tanks. Unfortunately, this information was limited. I saw no reports on German tanks larger or more powerful than the PzKw III and the PzKw IV with the short-barreled 75mm howitzer. We had no information about the German Panther tank, either, although I had read a newspaper account of the Tiger tanks that were used in North Africa against the 1st Armored Division. Because the M4 Sherman, with the 75mm gun in the turret, was far superior to the old M3, and because our knowledge of comparable German armor was limited, we felt that the M4 was a good tank.
Meanwhile, the Germans were replacing all the short-barreled 75mm guns on their Mark IV tanks with higher velocity guns, and they were developing the Panther and Tiger. The Sherman could not compare with these. American tank designers also failed to give proper consideration to the latest Soviet advances in armor. Their medium T34 and heavy Josef Stalin tanks were both equipped with more powerful guns, heavier armor, and wider tracks than the M4 Sherman.
The U.S. Army did finally develop the M26 Pershing tank, with heavier armor and wider tracks than the M4, and with a long-barreled 90mm gun. This tank was far superior to the Sherman and would have placed us on a more level playing field with the German armor. However, due to the arrogance of certain high-ranking officers it was recommended that this tank be given a low priority, and production concentrated on the M4 Sherman. Many observers at the time believed that had we had the M26 Pershing during the November 1944 offensive east of Aachen, we might have been able to break through the last vestiges of the Siegfried line, exit onto the Cologne Plain, and outflank the German troops building up in the Ardennes. Had this occurred, the Battle of the Bulge might never have taken place and the war would have ended months earlier. (pp. 175-176).
Saludos cordiales
JL
"Dioses, no me juzguéis como un dios
sino como un hombre
a quien ha destrozado el mar" (Plegaria fenicia)
