King Tiger armour effectiveness

[blazingPanzer]

I was playing a scenario from the Valkyries scenario pack the other night and noticed a strange event. I had ordered a single Pz company consisting of 7 king tigers to attack a US light flak company; this enemy unit was equipped with only 2 weapons capable of killing armour which were its 40 mm flak guns and bazookas. The tigers closed to approximately 200 m distance and then lost one of their vehicles to american fire (this instant is captured in the screenshot). I am confused as to how this is possible, as the 40 mm and bazooka can only penetrate 59 mm and 109 mm respectively at best, which should be no where near enough to penetrate the king tiger's 206 mm frontal plate; as can be seen from the picture this loss could not have been the product of a side shot as the tiger unit is directly facing its opponent. Perhaps the nightime/light fog conditions could have something to do with it, but this doesn't seem to make much sense to me.

 

[Rake]

Being relatively new and not entirely familiar with this game, I can only surmise that this would have to do with the actual footprints of the units involved. Given your stated night/light fog conditions and that the KT company is attacking along a wooded track, I would think it's altogether possible that a bazooka team could infiltrate the position for a flank/ rear shot.

Still, the likelihood of a K-Kill by a bazooka, while theoretically possible, is highly unlikely. In a quick search I was unable to find a documented instance of a K-Kill on a KT by a bazooka. I don't yet understand how the game would differentiate between a K-Kill or M-Kill, the latter of which was the cause of loss to many of the KT's in the Ardennes.

 

[Agema]

I think the game reflects tanks taking non-catastrophic damage that renders them combat ineffective - for instance immobilisation, critical gun damage, etc. The tank might not have been blown up but it needs repairs, and is out of the action. So generally, try to avoid close range engagements with tanks.

This is doubly important for the Germans, because they have accurate and high penetration guns and the armour (on the Panthers and Tigers, at least) is very effective; both advantages are vastly reduced at close range.

 

[john connor]

Closing to 200m with armour, in woods, in darkness, would seem to ask for some damage, and as Agema says, it might just be the track is off. But, aside from that, it's not a tactical simulator, so you placing a unit to face a threat does not mean that all units within that group will always be face-on to the threat. It's more a general representation, and as the engagement happens there will be movement etc that is all abstract in the game (you have to imagine it), so, for example, one of Tigers started to turn, exposed a flank or rear etc. So it doesn't look off to me. That said, though we can come up with explanations, it's always possible, also, that something is a bug. If it happens a lot then get a save and send to Dave, maybe?

Peter

 

[Daz]

I don't know exactly how the math is done behind the scenes, but a lot of things at this scale of simulation need to be abstracted.

In your example above for example the 7 Tigers would not be able to advance in line formation down that track through the woods.
It would only be wide enough to fit one with the others following in successive line behind.
The tanks would have been heard for quite some distance away. Plenty of time to put bazooka teams out on the flanks of the track.
As there is no infantry support for the tanks, the bazooka teams would have easily been able to stay concealed long enough, in the dark forest under a vail of fog, in order to get in a shot on the flank of the lead tank.

As I say, it doesn't actually happen like that in the game engine. Its just numbers being crunched. We need to use our imaginations to make sense of what numbers the Devs have had to plug in, to make an encounter like this make sense.
I think the realistic result of losing a heavy tank in this encounter, from an unsupported armoured attack, down a narrow track, through dark woods, in the fog, makes sense.
So I would say that the abstracted results that the game engine has spat out in this instance at least are working fine.

Here are some historic accounts between infantry verses tanks, in close terrain, during the battle of the bulge.
Note that these attack were supported by infantry, its just that most of the supporting infantry was killed by artillery.



The 1st Battalion refused to panic and set to work with bazookas against the flanks of the blinded tanks. One of the panzers was crippled, but the crew compartment proved impervious to bazooka rounds (perhaps this was a Tiger). So Cpl. Charles Roberts (Company D) and Sgt. Otis Bone (Company B) drained some gasoline from an abandoned vehicle, doused the tank, and lit the whole with thermite grenades. When German tanks moved into the Company A area, American artillery responded to the urgent call for help and within three minutes dropped in a concentration that stopped the assault

In the first contact at the crossroads east of Rocherath the German tanks were halted by a hasty mine field, but the rifle company made its most effective use of this defense by laying mines to protect the rear of the American position after the tanks had rolled by. The bazooka in the hands of the defending infantry proved extremely useful. During the dark hours, bazooka teams were able to work close to their prey under the cover provided by walls, houses and hedgerows. But, as in the case of the tank destroyers, most hits were scored against tanks which had paused or been stranded by the detonation of mines and high-explosive shellfire. In the various melees at the villages the German tank crews seldom escaped no matter what weapon was used against them. Most crewmen were burned as the tank blew up or they were cut down by bullet fire at close range. The 2d Division, like most veteran divisions, had armed itself beyond the limits of approved tables of equipment. Nearly every rifle platoon, as a result, had at least two bazookas, so that team play to distract and then destroy the target tank was feasible.

The morning fog was heavy, visibility almost nil. The American infantry let the tanks roll past, then tailed them with bazookas or turned to meet the oncoming infantry at close quarters with grenades, and even bayonets or knives. This first assault was beaten off, while a number of the German tanks were crippled or destroyed by bazooka teams stalking successfully under cover of the fog.

 

[Dave 'Arjuna' O'Connor]

What they said.

 

[blazingPanzer]

I agree with the posts above that losing even the heaviest AFVs in this sort of engagement is pretty likely in a real life scenario; what caused me to doubt the result was the assumption that in the game every subelement of a unit is contained within and facing the exact direction of the unit footprint box. Knowing that this is not the case I won't be trying such ill advised maneuvers in the future . Out of curiosity are all vehicle kills in CO2 catastrophic kills or does this figure count repairable/damaged vehicles as well, and if so is there any sort of repair/recovery system modeled? I understand this was an area where the Germans had a pretty significant advantage over their opponents as they possessed a significantly more efficient recovery system which enabled them to put many knocked out vehicles back into action, provided they maintained control of the ground at the end of a battle.

 

[Kurt]

The " kills " are not all catastrophic , just out of action . At the moment their is no replacement/repair element in CO2 , why not raise a new thread in " Feature Requests " .

 

[GoodGuy]

The 1st Battalion refused to panic and set to work with bazookas against the flanks of the blinded tanks. One of the panzers was crippled, but the crew compartment proved impervious to bazooka rounds (perhaps this was a Tiger). So Cpl. Charles Roberts (Company D) and Sgt. Otis Bone (Company B) drained some gasoline from an abandoned vehicle, doused the tank, and lit the whole with thermite grenades. When German tanks moved into the Company A area, American artillery responded to the urgent call for help and within three minutes dropped in a concentration that stopped the assault

In the first contact at the crossroads east of Rocherath the German tanks were halted by a hasty mine field, but the rifle company made its most effective use of this defense by laying mines to protect the rear of the American position after the tanks had rolled by. The bazooka in the hands of the defending infantry proved extremely useful. During the dark hours, bazooka teams were able to work close to their prey under the cover provided by walls, houses and hedgerows. But, as in the case of the tank destroyers, most hits were scored against tanks which had paused or been stranded by the detonation of mines and high-explosive shellfire. In the various melees at the villages the German tank crews seldom escaped no matter what weapon was used against them. Most crewmen were burned as the tank blew up or they were cut down by bullet fire at close range. The 2d Division, like most veteran divisions, had armed itself beyond the limits of approved tables of equipment. Nearly every rifle platoon, as a result, had at least two bazookas, so that team play to distract and then destroy the target tank was feasible.

The morning fog was heavy, visibility almost nil. The American infantry let the tanks roll past, then tailed them with bazookas or turned to meet the oncoming infantry at close quarters with grenades, and even bayonets or knives. This first assault was beaten off, while a number of the German tanks were crippled or destroyed by bazooka teams stalking successfully under cover of the fog.

This was, for a vital part, a close combat and small units engagement, with mainly the US 2nd Division's 38th Rgt. being involved, if I am not mistaken. House to house fighting, for both sides' inf troops, and a flanking attempt (after they had failed to advance on the town's streets) executed by the bulk of the German Tiger I tanks, while one of them kept trying to advance through the town. It's not quite clear whether it was a Tiger that got knocked out, as Pz IVs were also to support units in the area, and as it's well known that quite some accounts in unit diaries and AARs had declared Pz IV to be Tiger tanks (this goes for quite some AARs from events in Normandy '44 to events in 1945), as quite some inf grunts kept declaring suddenly charging/appearing German tanks to be Tiger tanks, on quite some occasions. One reason for this might have been the fact, that there were still Pz.IVs around that had received additional armor plates (bolted, welded later on, iirc) on their vertical front plates, but they had not received the Schürzen (side and turret skirts), which made them look more bulky/clunky, and the fact that a charging Panzer IV could still be a terrifying sight for a foot soldier (if compared to say a charging Sherman or StuG), if it was charging right on him.
Also, tank duels inside Rocherath "were fought from street to street; infantry fought from house to house", as John Toland sums it up correctly in "Battle: The Story of the Bulge". The bazooka teams got tail shots or side shots, at short distances (50 meters or less).

Now, in contrast, Peiper lost 1 King Tiger west of Büllenbach, for example, and I am not sure right now what kind of kill that was. The terrain was unfavourable for tanks, as Peiper reported after the war, but it was in the open IIRC, so only fire from US tank destroyers (which were in the area), AT guns or a mechanical failure could have been the reason for the total loss of that particular tank, but not AT inf fire.

Except for rare close combat fights during Market Garden, and some engagements during the Battle of the Bulge, Tiger II tanks tried to keep a favourable distance to their targets, to avoid inf ambushes, wherever possible, and to make the best use of their thick/superior frontal armor and superior effective view range. On the Eastern Front, single King Tigers killed 38-41 enemy tanks well outside the enemies' effective ranges, before running out of shells or fuel.

Now, regarding the particular fight in the game, a distance of 200 meters would be inside the effective range of a Bazooka, in theory, but in reality distances of 150 meters proved to be a challenge for a bazooka gunner, already. This engagement basically involves a tank unit charging or traveling on a road in the woods and meeting opposition in form of a roadblock (Bazooka gunners would not just sit on the street or hide behind single trees, as they would get cut down within a minute).

In reality, in daylight, the lead tank would have quickly identified the enemy presence (after the first Bazooka round was fired, at the latest), and the bazooka round would have failed to completely penetrate the thick frontal glacis of the King Tiger (150 mm of armor with a slope of 40 degrees), most likely. At night, bazooka teams could have let the King Tiger pass and attempted side or rear shots, but in this game instance, the units are clearly not next or on top of each other.

On top of that, the Bazookas' trigger mechanisms (changed to magnetic ones around 1943, afaik) and their rounds (and in particular their fuzes) were prone to arctic conditions (1944/45 was the coldest winter in 40 years), the War department stressed (Bazooka field manual, 1943) that rockets were not to be fired below minus 18 degrees Celsius (temperatures reached minus 40 degrees, IIRC), and the fuzes failed to ignite quite often for this particular reason, but also due to the design of the tip of the rockets.

On one occasion, a separated group of soldiers that happened to end up behind enemy lines in its jeep, which was equipped with a bazooka and a good number of rounds, had spotted a lone Stug advancing parralel to their road, and decided to engage the lone tank on its side/flank. Even though they had shots on the Stug's side at 80-90 degrees, all of the rounds that were fired (5-7) had failed to ignite on impact and just bounced, so basically just "dinged" the tank, while it was retreating slowly (and still showing its side). This problem still occured in Korea, as even with the "Super Bazooka" variant, plenty of reports complaining about the unreliable bazooka rounds had come up. With most of these engagements, attacks were carried out from positions inside houses, with enemy tanks (Russian models, even T-34 tanks) being attacked at point blank ranges, right in front or below the bazooka teams.

Even if you consider that the edges of the units' footprints in the game might actually mesh, so that distances could be below 200 meters in this particular game situation, Tiger II tanks - historically - usually put recon or light armor in front of their column when such terrain (roads through woods) was to be crossed. Peiper, for instance, put the King Tigers attached to his unit at the end of the column, where his column was spread over a length of 25 kilometers, eventually, at one or another point. King Tigers would not have traveled at night without employing a lead element.

For attacks, tank units in France, in 1940, and tank units in Russia, in 1941 and 1942, had performed large flanking or pincer movements and were followed up by infantry units, where the latter had to consolidate the pockets' edges, but in late 1944 a large amount of tank unit commanders started to fall back to something I would call "outdated" tank tactic, as they often tried to make sure that their charging tanks were closely supported by inf units, due to fears of losing precious tanks, making moves/progress slow and tanks vulnerable to aimed AT fire and hastily (often during the night or right before pending attacks) prepared mine belts, while attacks often stalled or were aborted due to the high losses among escorting inf units. For the most part, the King Tigers were not deployed like that, afaik.

I assume that in this game situation the particular tank unit is traveling and in column formation. I don't know the tank unit's composition, but in reality such units had recon or lightly armored advance party elements attached to it, which then screened the road ahead of the column, to avoid ambushes. Also, since the King Tigers were pretty much the slowest elements within the German battle tank pool, other elements in front would have passed the info regarding enemy presence, already. Single platoons may have been able to hide and let a lead tank pass, without getting detected, but not an entire company (as seen in the game).
Losing that King Tiger in the game does not appear to be realistic, unless the units were pretty much on top of each other.

From the top of my head, I cannot recall any historical report where an infantry unit of the size of a company and equipped with bazookas had managed to knock out a King Tiger coming down a long road in a frontal attack and at that distance, and with more King Tigers following behind.

During the initial onslaught in the Ardennes, German lead elements (recon tanks, or Pz IV and Pz V) had engaged such blocking units and the usual time frame to boot or remove the threats (inf with bazookas, AT guns) ranged from 2 to 15 minutes with few exceptions, even at night (some lead elements illuminated road sectors with flares), with the famous exception where 1 or 2 AT gun platoons held up a large tank unit, as well as with the exceptional (and well prepared/executed) defense at Elsenborn ridge, for instance, until Allied resistance stiffened later on.

 

[Kurt]

This was, for a vital part, a close combat and small units engagement, with mainly the US 2nd Division's 38th Rgt. being involved, if I am not mistaken. House to house fighting, for both sides' inf troops, and a flanking attempt (after they had failed to advance on the town's streets) executed by the bulk of the German Tiger I tanks, while one of them kept trying to advance through the town. It's not quite clear whether it was a Tiger that got knocked out, as Pz IVs were also to support units in the area, and as it's well known that quite some accounts in unit diaries and AARs had declared Pz IV to be Tiger tanks (this goes for quite some AARs from events in Normandy '44 to events in 1945), as quite some inf grunts kept declaring suddenly charging/appearing German tanks to be Tiger tanks, on quite some occasions. One reason for this might have been the fact, that there were still Pz.IVs around that had received additional armor plates (bolted, welded later on, iirc) on their vertical front plates, but they had not received the Schürzen (side and turret skirts), which made them look more bulky/clunky, and the fact that a charging Panzer IV could still be a terrifying sight for a foot soldier (if compared to say a charging Sherman or StuG), if it was charging right on him.
Also, tank duels inside Rocherath "were fought from street to street; infantry fought from house to house", as John Toland sums it up correctly in "Battle: The Story of the Bulge". The bazooka teams got tail shots or side shots, at short distances (50 meters or less).

Now, in contrast, Peiper lost 1 King Tiger west of Büllenbach, for example, and I am not sure right now what kind of kill that was. The terrain was unfavourable for tanks, as Peiper reported after the war, but it was in the open IIRC, so only fire from US tank destroyers (which were in the area), AT guns or a mechanical failure could have been the reason for the total loss of that particular tank, but not AT inf fire.

Except for rare close combat fights during Market Garden, and some engagements during the Battle of the Bulge, Tiger II tanks tried to keep a favourable distance to their targets, to avoid inf ambushes, wherever possible, and to make the best use of their thick/superior frontal armor and superior effective view range. On the Eastern Front, single King Tigers killed 38-41 enemy tanks well outside the enemies' effective ranges, before running out of shells or fuel.

Now, regarding the particular fight in the game, a distance of 200 meters would be inside the effective range of a Bazooka, in theory, but in reality distances of 150 meters proved to be a challenge for a bazooka gunner, already. This engagement basically involves a tank unit charging or traveling on a road in the woods and meeting opposition in form of a roadblock (Bazooka gunners would not just sit on the street or hide behind single trees, as they would get cut down within a minute).

In reality, in daylight, the lead tank would have quickly identified the enemy presence (after the first Bazooka round was fired, at the latest), and the bazooka round would have failed to completely penetrate the thick frontal glacis of the King Tiger (150 mm of armor with a slope of 40 degrees), most likely. At night, bazooka teams could have let the King Tiger pass and attempted side or rear shots, but in this game instance, the units are clearly not next or on top of each other.

On top of that, the Bazookas' trigger mechanisms (changed to magnetic ones around 1943, afaik) and their rounds (and in particular their fuzes) were prone to arctic conditions (1944/45 was the coldest winter in 40 years), the War department stressed (Bazooka field manual, 1943) that rockets were not to be fired below minus 18 degrees Celsius (temperatures reached minus 40 degrees, IIRC), and the fuzes failed to ignite quite often for this particular reason, but also due to the design of the tip of the rockets.

On one occasion, a separated group of soldiers that happened to end up behind enemy lines in its jeep, which was equipped with a bazooka and a good number of rounds, had spotted a lone Stug advancing parralel to their road, and decided to engage the lone tank on its side/flank. Even though they had shots on the Stug's side at 80-90 degrees, all of the rounds that were fired (5-7) had failed to ignite on impact and just bounced, so basically just "dinged" the tank, while it was retreating slowly (and still showing its side). This problem still occured in Korea, as even with the "Super Bazooka" variant, plenty of reports complaining about the unreliable bazooka rounds had come up. With most of these engagements, attacks were carried out from positions inside houses, with enemy tanks (Russian models, even T-34 tanks) being attacked at point blank ranges, right in front or below the bazooka teams.

Even if you consider that the edges of the units' footprints in the game might actually mesh, so that distances could be below 200 meters in this particular game situation, Tiger II tanks - historically - usually put recon or light armor in front of their column when such terrain (roads through woods) was to be crossed. Peiper, for instance, put the King Tigers attached to his unit at the end of the column, where his column was spread over a length of 25 kilometers, eventually, at one or another point. King Tigers would not have traveled at night without employing a lead element.

For attacks, tank units in France, in 1940, and tank units in Russia, in 1941 and 1942, had performed large flanking or pincer movements and were followed up by infantry units, where the latter had to consolidate the pockets' edges, but in late 1944 a large amount of tank unit commanders started to fall back to something I would call "outdated" tank tactic, as they often tried to make sure that their charging tanks were closely supported by inf units, due to fears of losing precious tanks, making moves/progress slow and tanks vulnerable to aimed AT fire and hastily (often during the night or right before pending attacks) prepared mine belts, while attacks often stalled or were aborted due to the high losses among escorting inf units. For the most part, the King Tigers were not deployed like that, afaik.

I assume that in this game situation the particular tank unit is traveling and in column formation. I don't know the tank unit's composition, but in reality such units had recon or lightly armored advance party elements attached to it, which then screened the road ahead of the column, to avoid ambushes. Also, since the King Tigers were pretty much the slowest elements within the German battle tank pool, other elements in front would have passed the info regarding enemy presence, already. Single platoons may have been able to hide and let a lead tank pass, without getting detected, but not an entire company (as seen in the game).
Losing that King Tiger in the game does not appear to be realistic, unless the units were pretty much on top of each other.

From the top of my head, I cannot recall any historical report where an infantry unit of the size of a company and equipped with bazookas had managed to knock out a King Tiger coming down a long road in a frontal attack and at that distance, and with more King Tigers following behind.

During the initial onslaught in the Ardennes, German lead elements (recon tanks, or Pz IV and Pz V) had engaged such blocking units and the usual time frame to boot or remove the threats (inf with bazookas, AT guns) ranged from 2 to 15 minutes with few exceptions, even at night (some lead elements illuminated road sectors with flares), with the famous exception where 1 or 2 AT gun platoons held up a large tank unit, as well as with the exceptional (and well prepared/executed) defense at Elsenborn ridge, for instance, until Allied resistance stiffened later on.

 

[Kurt]

Hey Gunnar , on a different subject , regarding the issue of the the K Grwr42 short barrelled 8cm mortar . I read that although originally intended to replace the 5cm mortar for Fallschirmjager units , it started to replace the standard Grwr34 in all German formations from 1942 . If true then how widespread was its issue in 1944-45 ? Did it represent 50% compared with the Grwr34 . I am guessing the short barrelled version would definitely be the organic mortar in rifle companies ?

 

[GoodGuy]

Hey Gunnar , on a different subject , regarding the issue of the the K Grwr42 short barrelled 8cm mortar . I read that although originally intended to replace the 5cm mortar for Fallschirmjager units , it started to replace the standard Grwr34 in all German formations from 1942 . If true then how widespread was its issue in 1944-45 ? Did it represent 50% compared with the Grwr34 . I am guessing the short barrelled version would definitely be the organic mortar in rifle companies ?

Hmm.. no.

The short-barreled k.GrW 42 (k = "kurz" = short, length: only 747 mm, weight: only 26 kg) was designed for and issued to Fallschirmjäger units exclusively, and it was produced in really low numbers:
Only around 1,591 pieces were produced in 1943.

Interestingly, even though the regular 5 cm mortars appeared to be rather useless at later stages of the war, as troops on all sides received support from bigger calibres, and even though it was pretty inaccurate, the disperson appeared to be 31 meters (depth/length) and 4 meters (width) at max distance (520 meters), quite some German inf units held on to them (production phased out in 1943 after 31,800 units had been produced) for the remainder of the war, even though they were supposed to dump them, as it took only 2 men to carry them and as they allowed for almost instant use, once they were assembled (instead of leveling the base plate and adjusting the mortar's elevation, one soldier would put a sand bag/rock under the base plate, and would then hold the upper part of the barrel and aim himself - for almost vertical fire on nearby targets - and then drop the round himself or would let another soldier drop the round into the barrel). Such use of the 5 cm mortars was often reported by GIs in Italy, a couple Medal of Honor credentials covering awards for actions in that theater mention such deployments, where German mortar teams hid in bomb craters, terrain depressions or trenches, and where they kept shelling advancing US platoons, or US units searching for cover in nearby craters, at distances of 50-150 meters, too.
The usual setup was then to suppress the GIs with MG fire, and plaster them with the 5 cm shells.
The 5 cm mortars were used throughout the war and had even received spikes under their base plates, for use on frozen ground (Russia), somewhere between 1942 and 1943.

The standard (long-barreled) "schwerer Granatwerfer 42" was almost a 100% copy of the Russian 120 mm Polkovoi Minomjot obr. 1938 (120 PM-38), which was captured by the Wehrmacht (in 1941) in large quantities. As I have outlined in one or another post here and in the old CO forums, the Russian mortars were pressed into service by the German Army, because their own 5 cm and 8 cm mortars were way inferior, way more inaccurate and because they lacked punch.

Since the German field manual for the captured 12 cm mortar carries the date 1st of November 1941, then this date, if first batches had not been issued before that date, has to be seen as (latest) official date of incorporation.

Now, even though the Granatwerfer 42 was a really close copy of the Russian mortar (which seemed to be a copy of a French mortar), the Germans applied some minor changes and the following major change: it received an axle/carriage which resulted in the troops praising its mobility, as it could be deployed more quickly than any other medium or heavy mortar of the period and as it could be towed by almost every vehicle in the German vehicle pool.

Also, Panzer-Grenadier-Regiments received Sd.Kfz with mortars mounted inside, where - initially - 8cm mortars were installed, but which were then replaced by the Granatwerfer 42 mortars, as authorized strength sheets then envisaged a Panzer-Grenadier-Regiment to feature 24 x 8 cm GrW and 4 x 12 cm mortars (on Sd.Kfz).
Since parallel production of the 8 cm and the 12 cm mortars was maintained until almost the end of the war, and since the production output of the GrW 42 was not sufficient to completely replace the 8 cm mortar, both mortars were present in such units. This goes for other units (eg. foot inf units), too.
Even though the Germans had captured those large quantities in 1941, quite some of them had been lost between 1942 and 1944, and even though they had started to produce a massive amount of 120-grenades, the production of the copy was lagging behind and never managed to replace stuff on a sufficient level.

The Germans planned to reorganize the MG Bns, to redesignate them "schwere Granatwerfer-Btl" (heavy mortar Bns) and equip them with the 12 cm mortars (no country designation, so it's not quite clear whether these were to be taken from the first production batches of the GrW 42 or whether these were to be taken from stocks of captured barrels) as Schwerpunkt support in 1942 already (the begin of implementation was earmarked for the 28th of August 1942 initially, but it seems like the assault on Stalingrad, and the subsequent Russian offensive later on, had disturbed the implementation of these plans, so that first organizational chart sketches date April 1943, and later, so the attempt to implement this must have started somewhere after April 1943.
But it seems like - at least in the main - (due to the low production numbers, see below) such dedicated s.GrW-Bns did not materialize before 1944.

Rough production numbers:
5 cm mortar : 25,842 (1939 - 1943)
8.1 cm mortar: 72,221 (1939 - 1945)
12 cm mortar: 8,461 (1943 - 1945)

Surprisingly, the German 8cm mortar (GrW 34) was even produced in 1945, the Army accepted deliveries of 1,553 8 cm-mortars in January 1945, 2,235 mortars in February and around 2,000 in March '45.

That said, the 12 cm mortar can be seen as an addition to the German arsenal, but not as comprehensive replacement, due to the relatively low numbers.
It's not quite clear whether this weapon mix (8 cm and 12 cm mortars) had been ordered due to the low production numbers of the 12 cm mortars, or if such organization was the result of a particular tactical thought process.
Since the 8 cm barrels were inferior and since they provided less accuracy/range, and since the 12 cm mortar output war relatively low, I tend to think that the Germans tried to equip as many units with the 120 mm as possible, so that the 8 cm mortars had to be kept.
There is no evidence for this theory, though, and the Germans also believed in the concept of having light and heavy sections (eg. light and heavy field guns), where then certain sections were employed (sometimes even combined) on a Bn level - in direct support of attacking companies, and others on a regimental level - to support entire Bns, respecively their sectors.

The initial idea for the Regiments was here, that the 12 cm mortar should partially replace the s.IG 33 - which were usually employed on a regimental level - in the heavy companies, because the production of such heavy inf guns involved an incredible amount of man hours and handicraft, and parts were numerous and expensive to produce, whereas a mortar was cheaper to produce and surely involved way less man hours.
For instance, the production of a light inf gun (le.IG 18), which required quite an amount of handicraft as well, involved 1,200 hours of labour.
The inability to fire (direct) flat trajectory shots was accepted, especially since less personnel was required to operate the mortar barrels.
It seems like the Germans had planned for a ratio of 2:1 (2 light pieces and 1 heavy piece), but that never materialized.

In general, such heavy mortars (as well as the Inf guns) were infantry assets of the Army ("Heer").
In 1943, and in Panzergrenadier-Divisions, the 4th Coy was kept and - just like in non-motorized inf units - was to be employed as HMG and/or GrW company. This heavy company was supposed to feature a heavy mortar platoon (120 mm), but few companies had actually managed to implement this change in 1943. That mortar was also supposed to replace the 75 mm le I.G. (inf gun), actually, but le IGs were still used until the end of the war.

The required strengths of 1944 and 1945 for Panzer-Grenadier-Divisions then envisaged to combine the GrW in a dedicated mortar coy for unarmored Grenadier units, featuring one heavy platoon (120 mm) and 2 light platoons (81 mm).
The org charts from that period also list the first appearance of an engineer coy that had partially transformed into an armored engineer unit, eventually, which was equipped with 2 HMGs and two 8 cm mortars, while it seems that the armored Grenadier Coys then lost their HMGs and were only issued two 8cm mortars each, but where then four 120 mm mortars were issued to the 4th heavy coy.

 

[Kurt]

Hmm.. no.

The short-barreled k.GrW 42 (k = "kurz" = short, length: only 747 mm, weight: only 26 kg) was designed for and issued to Fallschirmjäger units exclusively, and it was produced in really low numbers:
Only around 1,591 pieces were produced in 1943.

Interestingly, even though the regular 5 cm mortars appeared to be rather useless at later stages of the war, as troops on all sides received support from bigger calibres, and even though it was pretty inaccurate, the disperson appeared to be 31 meters (depth/length) and 4 meters (width) at max distance (520 meters), quite some German inf units held on to them (production phased out in 1943 after 31,800 units had been produced) for the remainder of the war, even though they were supposed to dump them, as it took only 2 men to carry them and as they allowed for almost instant use, once they were assembled (instead of leveling the base plate and adjusting the mortar's elevation, one soldier would put a sand bag/rock under the base plate, and would then hold the upper part of the barrel and aim himself - for almost vertical fire on nearby targets - and then drop the round himself or would let another soldier drop the round into the barrel). Such use of the 5 cm mortars was often reported by GIs in Italy, a couple Medal of Honor credentials covering awards for actions in that theater mention such deployments, where German mortar teams hid in bomb craters, terrain depressions or trenches, and where they kept shelling advancing US platoons, or US units searching for cover in nearby craters, at distances of 50-150 meters, too.
The usual setup was then to suppress the GIs with MG fire, and plaster them with the 5 cm shells.
The 5 cm mortars were used throughout the war and had even received spikes under their base plates, for use on frozen ground (Russia), somewhere between 1942 and 1943.

The standard (long-barreled) "schwerer Granatwerfer 42" was almost a 100% copy of the Russian 120 mm Polkovoi Minomjot obr. 1938 (120 PM-38), which was captured by the Wehrmacht (in 1941) in large quantities. As I have outlined in one or another post here and in the old CO forums, the Russian mortars were pressed into service by the German Army, because their own 5 cm and 8 cm mortars were way inferior, way more inaccurate and because they lacked punch.

Since the German field manual for the captured 12 cm mortar carries the date 1st of November 1941, then this date, if first batches had not been issued before that date, has to be seen as (latest) official date of incorporation.

Now, even though the Granatwerfer 42 was a really close copy of the Russian mortar (which seemed to be a copy of a French mortar), the Germans applied some minor changes and the following major change: it received an axle/carriage which resulted in the troops praising its mobility, as it could be deployed more quickly than any other medium or heavy mortar of the period and as it could be towed by almost every vehicle in the German vehicle pool.

Also, Panzer-Grenadier-Regiments received Sd.Kfz with mortars mounted inside, where - initially - 8cm mortars were installed, but which were then replaced by the Granatwerfer 42 mortars, as authorized strength sheets then envisaged a Panzer-Grenadier-Regiment to feature 24 x 8 cm GrW and 4 x 12 cm mortars (on Sd.Kfz).
Since parallel production of the 8 cm and the 12 cm mortars was maintained until almost the end of the war, and since the production output of the GrW 42 was not sufficient to completely replace the 8 cm mortar, both mortars were present in such units. This goes for other units (eg. foot inf units), too.
Even though the Germans had captured those large quantities in 1941, quite some of them had been lost between 1942 and 1944, and even though they had started to produce a massive amount of 120-grenades, the production of the copy was lagging behind and never managed to replace stuff on a sufficient level.

The Germans planned to reorganize the MG Bns, to redesignate them "schwere Granatwerfer-Btl" (heavy mortar Bns) and equip them with the 12 cm mortars (no country designation, so it's not quite clear whether these were to be taken from the first production batches of the GrW 42 or whether these were to be taken from stocks of captured barrels) as Schwerpunkt support in 1942 already (the begin of implementation was earmarked for the 28th of August 1942 initially, but it seems like the assault on Stalingrad, and the subsequent Russian offensive later on, had disturbed the implementation of these plans, so that first organizational chart sketches date April 1943, and later, so the attempt to implement this must have started somewhere after April 1943.
But it seems like - at least in the main - (due to the low production numbers, see below) such dedicated s.GrW-Bns did not materialize before 1944.

Rough production numbers:
5 cm mortar : 25,842 (1939 - 1943)
8.1 cm mortar: 72,221 (1939 - 1945)
12 cm mortar: 8,461 (1943 - 1945)

Surprisingly, the German 8cm mortar (GrW 34) was even produced in 1945, the Army accepted deliveries of 1,553 8 cm-mortars in January 1945, 2,235 mortars in February and around 2,000 in March '45.

That said, the 12 cm mortar can be seen as an addition to the German arsenal, but not as comprehensive replacement, due to the relatively low numbers.
It's not quite clear whether this weapon mix (8 cm and 12 cm mortars) had been ordered due to the low production numbers of the 12 cm mortars, or if such organization was the result of a particular tactical thought process.
Since the 8 cm barrels were inferior and since they provided less accuracy/range, and since the 12 cm mortar output war relatively low, I tend to think that the Germans tried to equip as many units with the 120 mm as possible, so that the 8 cm mortars had to be kept.
There is no evidence for this theory, though, and the Germans also believed in the concept of having light and heavy sections (eg. light and heavy field guns), where then certain sections were employed (sometimes even combined) on a Bn level - in direct support of attacking companies, and others on a regimental level - to support entire Bns, respecively their sectors.

The initial idea for the Regiments was here, that the 12 cm mortar should partially replace the s.IG 33 - which were usually employed on a regimental level - in the heavy companies, because the production of such heavy inf guns involved an incredible amount of man hours and handicraft, and parts were numerous and expensive to produce, whereas a mortar was cheaper to produce and surely involved way less man hours.
For instance, the production of a light inf gun (le.IG 18), which required quite an amount of handicraft as well, involved 1,200 hours of labour.
The inability to fire (direct) flat trajectory shots was accepted, especially since less personnel was required to operate the mortar barrels.
It seems like the Germans had planned for a ratio of 2:1 (2 light pieces and 1 heavy piece), but that never materialized.

In general, such heavy mortars (as well as the Inf guns) were infantry assets of the Army ("Heer").
In 1943, and in Panzergrenadier-Divisions, the 4th Coy was kept and - just like in non-motorized inf units - was to be employed as HMG and/or GrW company. This heavy company was supposed to feature a heavy mortar platoon (120 mm), but few companies had actually managed to implement this change in 1943. That mortar was also supposed to replace the 75 mm le I.G. (inf gun), actually, but le IGs were still used until the end of the war.

The required strengths of 1944 and 1945 for Panzer-Grenadier-Divisions then envisaged to combine the GrW in a dedicated mortar coy for unarmored Grenadier units, featuring one heavy platoon (120 mm) and 2 light platoons (81 mm).
The org charts from that period also list the first appearance of an engineer coy that had partially transformed into an armored engineer unit, eventually, which was equipped with 2 HMGs and two 8 cm mortars, while it seems that the armored Grenadier Coys then lost their HMGs and were only issued two 8cm mortars each, but where then four 120 mm mortars were issued to the 4th heavy coy.

Danke kamerad