W.I US T29 heavy tank moved into production

Unfortunate friendly fire

McNair while he did make a considerable difference in the us military including combined arms he did do some controversial matter too.

Overall, I consider him a net negative. He was a big fan of towed Anti-tank guns, vs SPG-- he spiked a number of GMCs that would have been useful, vs the overly heavy towed 3" and underpowered 57mm that struggled in Italy and France.Then his whole incorrect take on Tank Destroyers.

McNairs main influence was during his first year as head of AGF in 1942. The legislation allowing Marshal to reorganize the Army gave him or his head of AGF a wide window to unclog numerous buercratic problems that had been holding up many details in mobilization. McNair got the question of division organization & equipment settled so training could continue with some certanity in those and doctrine. Right or wrong his decisions in 1942 got the mobilization, equipment, training accelerated & put the readiness of the ground combat forces well ahead of where it would otherwise have been. McNair did a fair job of it in 1942, probably the error was in leaving him in place too long. Replacing him with a corps or Army commander from overseas in early 1943 might have been the better choice.

Many of the doctrines McNair wrestled with were inherited, and already signed off & difficult to alter. The TD doctrine had originated in latter 1940 & was a full blown 'Corps', like Armor, or Artillery by mid 1941. In any case the field commanders did their own ad hoc alteration of TD doctrine & the 1941-42 doctrine was effectively dead in the ETO in 1942. Ditto for the similar doctrine for the independent tank battalions. With so many Armor divisions on hand it was unnecessary to pool the independent battalions into tank or TF 'Groups'. That the field commanders were no requesting these Group HQ from the US during 1943-44 says a lot. They did accept Group HQ for engineers & artillery & others as those made sense in terms of how they were fighting the battles in Scilly, Italy, and France, but the division, corps, and army commanders preferred to distribute the TD & Tank battalions within the divisions.
 
His idea with towed AT was retrograde, that they should also charge towards the sound of the guns in Napoleonic fashion to setup would-be killboxes, towed either by lightly armored halftracks or high speed tractors.

One of the reasons US ATG units had such high casualties in Italy and France.

These tactics worked in the 1941 maneuvers against Devers, due to rules in place, that ATguns could only be destroyed by overruns, not by simulated HE or MG fire. Germans didn't play by those rules.

Neither did many field commanders in those exercises. They saw through the error of the umpires & developed other doctrines. As it was only 12 Towed TD battalions were formed, out of 60+. Well before 1944 the decision to stop organizing the towed TD battalions was taken.
 
Neither did many field commanders in those exercises. They saw through the error of the umpires & developed other doctrines. As it was only 12 Towed TD battalions were formed, out of 60+. Well before 1944 the decision to stop organizing the towed TD battalions was taken.
In 1942, Marshall forced McNair to include the GMCs that General Bruce wanted over towed guns when FM18-5 was being formed

Bruce wanted the T-42, then T-50 that in time would become the T-67/T-70 and then M18, but AGF ruled in favor of the M10 with the 3" gun being prioritized.

Here's what Bruce was thinking in May, 1942
T42%2BGMC.png
M3 Stuart bits with a 3" gun, but that was too much gun for for the Armored Board to be happy with
Back to planning.

M8A1 January 1943 an idea for an interim TD to be made till the M18 would be in production in early 1944
M8A1%2B%25282%2529.png

the M8 GMC with 75mm howitzer replaced with 75mm cannon. Still too much gun was claimed, but not backed up in testing
T-49 Buick's first attempt April 1942
T67%2BGMC%2B%25281%2529.jpg
57mm gun, twin Buick Straight Eight power. Closed turret. Coil spring suspension. slightly faster than the above from more powerful Buick engines(330hp) than the twin Caddy setup. 51mph was claimed, but got 38mph in tests
T-67
More power was desired, so got the Continental R-975 radial, dropped the bow MG, and got McNairs beloved open top turret with a 75mm gun. February 1943
This is the picture after the 75mm gun was replaced with the new 76mm wonder gun, before barrel was shortened to resolve a breech inbalance later that year
T67%2BGMC%2B%25282%2529.png

T-70
M18%2BHellcat%2B%25283%2529.png

almost the M18. The above with new turret shape and torsion bar suspension, done in April 1943. There was some talk of making this the next light tank to replace the M5, but rejected for the open top.
over 2500 were built from when it was Standardized in March 1944 to October 1944, when production was curtailed
 
To be fair, everyone's ATG units everywhere had high casualties.

But the towed AT units had higher casualties than the GMC equipped battalions
Back to the towed v. SPG

March 31, 1943, AGF ordered the conversion of fifteen battalions then in training at Camp Hood from self-propelled to towed. Eventually, half of all tank destroyer battalions were converted to towed gun, the opposite of what the Germans and Soviets were doing at that point of the war, going to SPGs.

Battalion commanders in Italy were unhappy with this, as the 3" towed was near useless in what the M10 had been doing, providing direct fire support to infantry, as well as indirect fire. Unlike the M10s, the towed 3" had no provisions for indirect fire, as all M10s had the M9 quadrant, and used enough that they M10 were wearing out gun tubes at rates far higher planned for

EDIT: found this factoid for effectiveness
Among the tank destroyer battalions assigned to First Army during the Normandy fighting, towed battalions on the average accounted for 5.8 enemy tanks and 4.0 pillboxes each, whereas the average self-propelled battalion in Normandy destroyed 22.5 panzers and 23.2 pillboxes.

again, with far higher loss rates for towed. In the aftermath of the Bulge, 1st Army of 67 TD losses, 65 were towed.
 
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