German Tank Intel 1944

 "Top Secret

Inspector General of the Tank Forces
#046/44 Top Secret

June 26th, 1944

Copy 1 out of 5

Notes on the report to the Fuhrer

[...]

Based on information received at 2:00 on June 25th from Tank Group West and Colonel Emichen, the following picture is formed on English and American tanks:

1. The new Cromwell tank is armed with one 75 mm L/34 gun. The American Sherman tank used to be armed with a 75 mm L/40 gun and now has a longer 76.2 mm L/52.8 tank gun (previously used on the M10 SPG).

Kotin's Bobtail

In early 1943 the Red Army Main Armoured Vehicle Directorate (GBTU) and People's Commissariat of Tank Production (NKTP) agreed that the age of the KV-1S is coming to an end. Instead, the IS-1 (233), a further development of the KV-13, was to be produced in Chelyabinsk. This tank had the same firepower, but was more mobile and better protected. However, the experimental IS-1 was too unrefined and suffered from assembly issues. In addition, trials of the German Tiger tank showed that the Red Army was in need of a tank with an 85 mm gun. This was how the KV-85 was created, the last mass produced tank in the KV family.

The KV's Last Bow

It is often the case in many nations that instead of new tanks, industry preferred improved versions of tanks that were already in production. The Soviet tank industry was no exception in this regard. That was the start of the history of the T-60, for example. Factory #37 proposed that an improved T-60 with a 45 mm cannon and improved armour be built instead of the T-70. That time the gamble didn't succeed, and the T-45 remained experimental. In 1942-44, a the story repeated itself with the heavy KV tank, which brought to life the KV-100 and KV-122 tanks, the tale of which this article will tell.

An Opponent for the Tiger

The capture of two Tiger tanks by the Red Army on January 18th, 1943, had a significant impact on Soviet tank building. Trials of one of the tanks revealed an unfortunate fact: the F-34 76 mm gun, the main weapon of Soviet tanks, could not penetrate the side. The reaction to this result was swift. Designers were tasked with developing a more powerful tank gun immediately. It was to be installed in the KV-1S heavy tank.

KV-85 Turret Upgrade

"To the Chief of the GBTU Tank Directorate, Major-General of the Tank Engineering Service, comrade Afonin

The senior military representative of the GBTU at the Kirov Factory, Engineer-Lieutenant-Colonel Markin reported the following to me on August 31st over radio, 1943 (via comrade Davidenko).

A number of mistakes were made in the KV-85 blueprints, which resulted in the following:

New Heavy Tanks, 1943

"To the Chief of the GBTU TU 6th Department, Regional Engineer at the Kirov Factory

July 5th, 1943

I report on the experimental work performed at factory #100 during June of 1943.

The most attention was paid to Objects 237 (experimental IS tank) and 239 (KV-1S tank with an IS tank turret and 85 mm gun).

Kirov Factory 1941-1945

Any company likes to toot its horn about its accomplishments, and the Kirov Factory is no exception. Here are posters commemorating their work during the Great Patriotic War:

"Kirov factory in the Patriotic War. Ural, 1941-1945"

"During the war, the factory created 13 types of heavy tanks and SPGs.

• KV-2 tank, 1940, before the war.
• KV-1 tank, 2371 produced in 1941-1942
• KV-1S tank, 1106 produced in 1942-1943
• KV-8 flamethrower tank, 42 produced in 1942 

• KV-8S flamethrower tank, 25 produced in 1942
• SU-152, 671 produced in 1942-1943
• KV-85 tank, 148 produced in 1943
• T-34 tank designed at factory #183, 5094 produced
• IS-85 tank, 107 produced in 1943
• ISU-152, 1875 produced in 1943-1945

• ISU-122, 1435 produced in 1944-1945
• ISU-122S, 475 produced in 1944-1945
• IS-2 tank, 3380 produced in 1944-1945
• IS-3 tank, 130 produced in 1945
• 701 tank, 1944-1945, recommended for adoption by the army

In total, the factory built 16859 tanks and SPGs during the war."

Upgunning

"Decree of the State Committee of Defense #3289ss
Moscow, Kremlin
May 5th, 1943

On the issue of increasing the firepower of tanks and SPGs.

In connection with the actions described in decree #3187ss issued on April 15th, 1943, the State Committee of Defense decrees that:

1. The NKV (comrades Ustinov and Grabin) and NKTP (comrades Zaltsmann and Kotin), factory #9 (comrade Gonor) and Kirov factory (comrade Dlugach) must design blueprints, produce, and install an 85 mm gun with ballistics identical to the existing AA gun into two KV-1S tanks and two experimental IS tanks, and deliver them for government trials by July of this year. The commander of the Armoured and Mechanized Forces of the Red Army (comrade Fedorenko) and GAU chief (comrade Yakovlev) must perform trials and deliver their conclusions to GOKO by July 10th of this year.
2. The NKV (comrades Ustinov and Grabin) and NKTP (comrades Zaltsmann and Kotin), factory #9 (comrade Gonor) and Uralmash (comrade Muzrukov) must design blueprints, produce, and install 85 mm guns with ballistics identical to the existing AA gun into two SU-122 SPGs and deliver them for government trials by July 1st of this year . The commander of the Armoured and Mechanized Forces of the Red Army (comrade Fedorenko) and GAU chief (comrade Yakovlev) must perform trials on the "SU-85" and deliver their conclusions to GOKO by July 10th of this year.
   UZTM drector comrade Muzrukov must send intermediates to factory #9 to produce experimental 85 mm guns to be fitted into the KV-1S, IS, and SU-85.
3. Factory #9 (comrade Gonor) and Uralmash (comrade Muzrukov) must prepare for production of an 85 mm tank gun and SPG gun without awaiting results of trials.
4. NKV (comrades Ustinov and Grabin) and NKSM (comrades Akopov and Slonimskiy) in cooperation with the commander of the Armoured and Mechanized forces (comrade Fedorenko) and GAU (comrade Yakovlev) must provide GOKO with conclusions regarding the 76 mm SPG proposed by TsKB and NATI.

Chair of the State Committee of Defense, I. Stalin."

RGASPI 644-2-165

85 mm Guns

Rival D-5 and S-31 guns might appear identical to the casual observer, but in reality, they had many subtle differences. The following data sheet contains the some data values regarding the KV-85 and IS-1 tanks that reveals some of them.

	IS tank, S-31 gun	IS tank, D-5 gun	KV-1S tank, S-31	KV-1S tank, D-5
Tank length	8460	8420	8210	8450
Tank width	3060	3060	3270	3270
Height (gun horizontal)	2700	2700	2600	2600
Height (gun elevated)	3280	3160	2600	3365
Clearance	380	380	380	400
Width between tracks	3060	3060	3265	3265
Track in contact with ground, length	4540	4700	4600	4600
Track in contact with ground, width	650	650	650	650
Vertical gun angle	-2 to +21	-3.5 to +22	-3.5 to 15	-2.75 to 23
Horizontal gun angle	360	360	360	360
Bore axis height	1900	1945	2070	1965
Gun dead zone (m)	50	23	42	35
Shell mass	AP: 9.2 kg HE: 9.54 kg
Total round mass	AP: 15.85 kg HE: 16.2 kg
AP muzzle velocity	800	800	800	800
Muzzle energy (ton-meters)	300	300	300	300
Penetration at 1000 meters at a 30 degree angle	83-98 mm

CAMD RF 38-11355-1529

As we can see, there are some differences in the size of the tanks that accommodate the gun, as well as various features, most notably gun depression. The IS can depress the D-5 more than the S-31, and even though the KV-85 can depress the S-31 slightly more, the higher bore axis gives that gun a much larger dead zone. Additionally, 15 degrees of gun elevation is quite unacceptable for a breakthrough tank that is expected to fight in urban conditions.

Mobility Trials Part 3

This one is less of a complete report, and more a mishmash of off-roading and various associated activities I have accumulated.

CAMD RF 81-12086-97

"Figure 13. The moment before fording.

Figure 14. The moment before fording. The tractor begins tilting forward at a point before the third road wheel."

These two photographs are from trials of the Ya-13F light artillery tractor. While it is not particularly important to know at what point a tank begins tilting forward as it enters a sharp incline, a vehicle that is meant to be towing something behind it is a different matter entirely.

Towing a gun? Easy. What about towing a tank?

CAMD RF 38-11355-2350

"Towing.

Towing was done twice, after the tank travelled 432 km and 767 km. The total distance of towing was 20 km. In the first case, an IS-122 and a KV-85 were towing an IS-122. In the second, an IS-122 towed an IS-122.

In both cases, the tank was towed over a dirt road trampled by tanks, and partially on an asphalt highway covered in packed snow, at 1st and 2nd gear, with external temperature between -5 and -9 degrees.

During towing, the engine's temperature was normal. The water temperature stabilized at 65 degrees. The oil temperature stabilized at 72 degrees.

Photo #27: IS-122 and KV-85 tanks tow an IS-122 tank on a road trampled by tanks."

CAMD RF 38-11369-351

A SU-100 undergoing mobility trials, showing the perils of a gun that is too long on bumpy terrain. The end of the gun is covered to prevent mud from getting in, but the sack cannot hide the distinctive shape of the muzzle brake. This is no ordinary SU-100, but a SU-122P, a SU-100 with a D-25 gun.

The sack was there for a very good reason.

CAMD RF 38-11369-541

"Fig. 2. The 122 mm SPG D25-SU-122P hits the ground with its barrel when descending from a bump with the gun elevated at 12 degrees."

KV-100 Trials

Not much is know about the KV-100, just one photograph of a KV-85 with an S-34 gun, only that it did not make it into production. Here are some pretty good reasons why.

"To the Chief of GAU KA, comrade Yakovlev
Commander of the Armoured and Mechanized Forces, comrade Fedorenko
Copy to the Narkom of Armament, comrade Ustinov

The NKTP received:

1. A report on the gunnery trials of the S-34 100 mm gun installed in the KV-85 tank and
2. A conclusion of the commission based on results of the gunnery trials.

Having examined the documents of the commission, the NKTP deems it necessary to make the following comments:

1. Even though the notes claim representatives of the NKTP were present at the trials, that does not represent reality, as the NKTP was not invited to the trials.
2. The tank turret was not equipped with an an ammunition rack, spare parts and instruments, observation devices, and was not balanced. The resulting trials are unconvincing and incomplete.

In specific:

1. The established rate of fire cannot be accepted, as shells were not retrieved from an ammunition rack, but stacked in the turret bustle. Firing was performed with the hatches open, and the crew was especially trained, which should not be done during normal rate of fire trials. The commission claims that placing the ammunition on the floor is undesirable, considering the weight of 100 mm shells, but then it is not clear where the commission proposes this ammunition be placed, as a large ammunition rack on the floor is a common feature of all tanks.
2. Firing from the move was ineffective, the causes of which were not established. It is known that firing from the move is an exceptionally important feature of a tank.
3. The commission did not perform measurements of turret rotation on a slope. Considering that the gun turned out unbalanced and the turret was heavy after installing a 100 mm gun (the commission remarks on difficulty when turning the turret), it can be determined that the installation of an S-34 in the tank causes serious balance issues for the turret.

Aside from these problems, the commission itself pointed out several negatives, such as the cramped loader and gunner workspaces, the necessity to move the turret traverse mechanism, replacement of the sight and observation devices, ventilation of the fighting compartment, etc.

After all this, it is a little strange to see that the commission concludes that the S-34 100 mm gun should be adopted into use in tanks and SPGs.

The NKTP considers that these trials can be considered trials of the gun only, and do not indicate the possibility of installing the gun into a tank, as no complete effort was made to install the gun into a tank. The NKTP cannot agree with the commission's conclusion.

People's Commissar of Tank Production, Malyshev

February 9th, 1944"

CAMD RF 38-11369-490