U.S. Smoke as Offensive Weapon

[rexford]

Being over 50, things sink in very slowly most of time. The Sept.-Dec. 2000 issue of AFV News had what appears to be one of the premier articles on U.S. smoke shell usage. The article is entitled:

AMERICAN SMOKE: An Underdog Battles the Big Cats, is by Michael Duplessis, and is a great read from start to finish.

A summary follows:

1. While the Eisenhower report destroys the comparative worth of most U.S. equipment compared to German, American smoke shells get an A+. Report site is at: http://www.hitechcreations.com/ubb/Forum9/HTML/000686.html

2. American tankers used smoke aggressively and offensively. Smoke shell direct hits on panzers could blind for as long as 4 minutes. Smoke would be carried in barrel as ready round in case a threat suddenly appeared. 6 of 15 ready rack rounds could be smoke.

3. German tankers on record as stating that American smoke rounds were excellent and exceptionally accurate. The exact phrase they used is "maddeningly accurate".

4. White phosphorus is not a Sherman tank standard ammo load but was designed for M1A1 Pack Howitzer, and it could be chambered by 75mm Sherman M3 gun. WP is not listed on the gun tables in Hunnicutt's SHERMAN.

Great accuracy in firing smoke rounds is an odd one. The 75mm smoke round weighed 3 kg (6.6 pounds compared to about 15 for APCBC), had a flat nose (really poor ballistically but avoids digging into ground), and was fired at 850 fps (259 m/s) which assures a high trajectory and poor first shot hit probability. Hitting a Tiger on the fly with a smoke round at 600m might take quite a few shots, if one could see through the smoke cloud.

We never use Sherman smoke rounds in our miniatures games, and that really may not be very realistic. Based on Duplessis' article smoke rounds were the mainstay of many tanks when they came across, or were attacked by heavy German armor. The only consolation for the panzer guys is that American smoke seems to only become available during and after June 1944.

We believe that the large kill ratio's for the Tigers in Nord Afrika in tank battles was helped by an absence of American smoke ammo for the Sherman, plus some problems with Sherman optics and training and crew experience and on and on.

What is perplexing is that there are many AAR where Shermans pelted Panthers and Tigers with armor piercing rounds and HE shells and nothing is said about smoke being flung around. There would almost seem to be wide variations in the degree to which smoke was valued and used from unit to unit.

Were smoke rounds used in a uniform manner between American units?

How wide would a smoke cloud typically get in a light wind? How long till smoke cloud develops and would block line of sight and fire? Duplessis indicates that HC smoke shells did not burn hot so they stayed close to the ground.

We're going to give our Shermans 4 or 5 smoke rounds apiece in some miniatures games and see how the panzers do. Or else we'll just stick to pre-6/44 games.

[dragonwagon]

Hmmm, interesting indeed. I loved to use smoke back in my ASL days . Works well in this game as well, if not better. Smoke , use it well , use it often..........

[Jeff Duquette]

From: Belton Cooper Death Traps, The Survival of an American Armored Division in WWII" Cooper was an ordnance officer serving with the 3rd Armored Division.

<blockquote>quote:</font><hr>Following General Rose's death, confusion was rampant among our leading elements. The general was trying to get Task Force Doan to secure our left flank when he was struck down. German groups of tanks and infantry counterattacked our task forces whenever possible. One major engagement just south of the Paderborn airport exemplified the tragic inferiority of our tanks".

One of our columns proceeded up a slightly inclined straight road. A narrow, winding road met the straight road about half a mile from the point where our column entered it. Heavily wooded, rolling hills lay on the right side of the road, and a level, open field was on the left with woods set back about three hundred yards. The column consisted of a company of M4 Sherman tanks followed by a company of armored infantry in half-tracks. These were followed by several GMC trucks and Jeeps and three M36 tank destroyers. Suddenly, seven King Tiger tanks appeared along the crest of the forward slope on the left side. As the tanks advanced toward our column, they turned to the right into a column formation and opened fire. We had no time or room to maneuver, and the Shermans could not utilize the advantage of our gyrostabilizers. Three more King Tigers emerged from the hilly woods road to the right. Our tankers and infantrymen were faced with their worst fear: to be caught in the open by King Tiger tanks at close range, without the ability to maneuver or seek cover.

The seven King Tiger tanks on the left proceeded down the entire length of the column, then turned around and came back. At extremely close range, a hundred yards or less, they raked the column from stem to stern. Some observers said it was more like a naval engagement than land warfare. The infantry immediately took cover in the ditches on both sides of the road. One of the Sherman tanks, with a 76mm gun, broke out of the column and took cover behind a small stucco farm building to the left, just off the road in about the middle of the column. As the Tigers came down on their first pass, the Sherman crew swung their 76mm gun 180 degrees to the rear and let go at close range. The Tiger's thinner armor over the engine compartment was penetrated, and the tank started to burn. The victory for this brave crew was short-lived, however, because the Sherman was knocked out by another Tiger on its return pass.

Although the entire column was trapped, some of the veteran crews stayed cool and utilized their advantages. One of the crews of an M4 Sherman with a short-barreled 75mm M2 gun was near the middle of the column when the three King Tigers appeared on the right side. The alert tank commander immediately saw two possibilities. First, he knew that the King Tiger had a slow traverse, and it would be extremely difficult and time-consuming for him to swing the turret and elevate the gun to zero in on him. Next, our tank commander knew that an armor-piercing shot from his low-velocity 75mm would just bounce off the King Tiger.

In a split second he told his gunner to load a white phosphorus round. It struck the glacis plate right above the driver's compartment with a blaze of flames and smoke. Although there was no possibility of penetration, the shock in the tank must have been terrific. The entire faceplate in front of the turret was covered with burning particles of white phosphorus which stuck to the sides of the tank. The smoke engulfed the tank, and the fan in the engine compartment sucked the smoke inside the fighting compartment. The German crew must have thought the tank was on fire and immediately abandoned it. Although the tank suffered little damage, had the crew stayed inside they would have been overcome by the deadly fumes. The Sherman immediately turned its gun on the second tank in the column and fired white phosphorus, with the same result. Although the ingenious tank commander knocked out two King Tiger tanks (without ever getting a penetration), his tank was then knocked out by another Tiger.

The King Tigers on the left proceeded all the way to the end of the column, where they knocked out one of our M36 tank destroyers, which blocked the rear of the column. The lead tank in the column had already been knocked out and trapped the entire column. As the German tanks returned to the front of the column, they swung their guns around to the other side and picked off the remaining tanks and half-tracks. It was like shooting ducks in a pond. The remaining King Tigers withdrew, leaving our entire column bleeding and burning.

When our maintenance crews arrived on the scene, we found a catastrophe. The Germans had knocked out seventeen M4 Sherman tanks, seventeen half-tracks, three GMC trucks, two Jeeps, and one M36 tank destroyer. The column had been annihilated. Fortunately, the personnel casualties had not been as high as the appearance of the wrecked column indicated. The German tanks were so close that the machine guns in the turrets would not depress low enough to reach the men in the ditches. We immediately started dragging back those vehicles that had not been totally burned. The burned-out vehicles were pushed off to one side of the road and abandoned.<hr></blockquote>

[ 12-04-2001: Message edited by: Jeff Duquette ]</p>

[rexford]

When Sherman tanks with 75mm fired smoke rounds at a target that was estimated to be at 600m, would they try to drop the round in front of the target and thus estimate range at 600m but set first shot for 100m or 200m less to avoid firing over the target range. We're developing a detailed set of armor miniatures and want to give smoke use a good system, so detailed info would be very valuable.

I have FM17-12 for Tank Gunnery but it is dated April 22, 1943, prior to availability of smoke for Sherman tanks.

One other question, why did Americans wait so long to develope smoke? One source I have says no Sherman smoke till June 1944. German 75L24 had smoke from start of war, so did StuG III. Advanced Squad Leader indicates that British tanks with 75mm gun (including Grant, Lee, Shermans) always had the possibility of carrying and using smoke. Yet Americans wait till Normandy. Anyone know why?

Not having smoke would place American Shermans in a less desirable position than British when they faced Tigers and PzKpfw IV in Nord Afrika.

[Louie the Toad]

I am curious to know what happened to the commander of the allied column. Seems like he completely forgot about Recon.

Curious Toad

[Simon Fox]

<blockquote>quote:</font><hr>Originally posted by Louie the Toad:

I am curious to know what happened to the commander of the allied column. Seems like he completely forgot about Recon.<hr></blockquote>Good point. Recon assets can get spread pretty thin sometimes, although missing that number of KTs does seem like a mega stuff up. Villers-Bocage is another example of a recon stuff up, although a few less Tigers were 'missed' there, critical recon assets of the units involved were still in the UK in that instance.

[Spook]

Steve Zaloga's "Lorraine 1944" also relates how the US 4th Armored Division in the Arracourt tank battles similarly utilized WP smoke rounds as to cause Panther tank crews to bail out, so to escape the fumes that the German tanks' ventilation systems had drawn in.

[offtaskagain]

Wasn't the WP trick used at Trois Points too?

[Captain Wacky]

For a more in-depth analysis of the use of smoke throught WWII armored combat, try here:

http://www.under-tec.com

[offtaskagain]

<blockquote>quote:</font><hr>Originally posted by Captain Wacky:

For a more in-depth analysis of the use of smoke throught WWII armored combat, try here:

http://www.under-tec.com

<hr></blockquote>

You are an evil man Wacky.

[Captain Wacky]

<blockquote>quote:</font><hr>Originally posted by panzerwerfer42:

You are an evil man Wacky.<hr></blockquote>

Evil, yes-but funny

[rexford]

Thanks, Cap Wacky.

[rexford]

When Advanced Squad Leader indicates that Grant, Lee and Sherman tanks in British use had smoke rounds from the very start of their use, this implies that the British made the smoke ammunition and would have started as soon as their acquisition of 75mm armed tanks was envisioned. Cause the U.S. did not use 75mm smoke till Normandy, if ASL is correct.

Can anyone verify that the British made 75mm smoke rounds during 1942 and made it available to their U.S. built tanks?

Thanks.

[Brian]

<blockquote>quote:</font><hr>Originally posted by rexford:

When Advanced Squad Leader indicates that Grant, Lee and Sherman tanks in British use had smoke rounds from the very start of their use, this implies that the British made the smoke ammunition and would have started as soon as their acquisition of 75mm armed tanks was envisioned. Cause the U.S. did not use 75mm smoke till Normandy, if ASL is correct.

Can anyone verify that the British made 75mm smoke rounds during 1942 and made it available to their U.S. built tanks?

Thanks.<hr></blockquote>

I was under the impression that the the 75mm tank gun was in fact developed from the 75mm field gun, which in turn, for the USA at least, had its roots in the venerable and famous French 75 of 1897. Hogg's British and American Artillery of WWII states that a smoke round existed for the US 75mm Field Gun - the "Complete Round, Shell, Chemical, 75mm, M64". If one then consults his companion book, Allied Artillery of World War One, which is unfortunately not quite as informative as WWII one, one finds that indeed, a smoke round for the French and by extension, US 75mm did exist in WWI.

Therefore, I'm rather surprised to find that the US armoured forces weren't utilising that round until late in WWII.

As for the British, Hogg mentions that they took on, in the dark, desperate days of 1940, any sort of gun they could lay their hands on, including both French and US 75mm Field Guns, as well as others, in the same calibre which various firms had manufactured for export. He doesn't explicitly discuss the ammunition but one could well presume that these weapons would have either been supplied with ammunition, also intended for export or imported from the US.

I'd suggest that these could well have been the source of the smoke rounds for the British 75mm armed tanks. Just as it appears perhaps the British were the source for 57mm HE rounds, at least initially.

Oh, and BTW, the smoke round, M64 weighed more than the normal HE or AP rounds, so its range was reduced in comparison.

[Enoch]

I have found the references to the use of smoke by US forces very limited. This is true for not only the use of smoke by armored forces but also artillery smoke. Perhaps the use of artillery smoke was so routine that it didn't warrant special mention. I have read numerous accounts of advances across open terrain that would seem to beg for smoke to cover the advance. I'd be interested if anyone has more info on the us of artillery smoke to cover an advance.

[rexford]

Thanks for great info, which is appreciated.

Michael Duplessis' article has 3 kg for M89 HC smoke round, and 3.3 kg for WP, as opposed to nearly 6.8 kg for 75mm APCBC-HE-T.

Combining light weight, flat nose and low muzzle velocity (850 fps for HC, about 925 fps for WP), makes first round direct hits problematic

The possibility of the British having 75mm smoke for French 75 available for Grants, Lees and Shermans is a very good comment.

I will ask Robert McNamara about his smoke recommendations in Advanced Squad Leader.

Thanks again for several good responses.

[JonS]

I seem to recall that in the desert the Brits had some problems with ammo for the Grants. Convieniently they had just overrun Vichy French Syria(?), and with it large stocks of French 75mm ammo.

A British artillery (or ordanance?) officer fiddled around with the fuses to get a reliable round. Now the point of this is that I think they were smoke rounds - though it could have been HE I suppose.

Apologies for being so vague, but hopefully this will jog someone who has a better memory than I.

Regards

JonS

[ 12-06-2001: Message edited by: JonS ]</p>

[Kanonier Reichmann]

<blockquote>quote:</font><hr>Originally posted by JonS:

I seem to recall that in the desert the Brits had some problems with ammo for the Grants. Convieniently they had just overrun Vichy French Syria(?), and with it large stocks of French 75mm ammo.

A British artillery (or ordanance?) officer fiddled around with the fuses to get a reliable round. Now the point of this is that I think they were smoke rounds - though it could have been HE I suppose.

Apologies for being so vague, but hopefully this will jog someone who has a better memory than I.

Regards

JonS

[ 12-06-2001: Message edited by: JonS ]<hr></blockquote>

I thought it was an ingenious Aussie who devised a way to utilise that captured French ammo but hopefully Brian, whose knowledge I'm sure surpasses mine on this subject, will either confirm or deny.

Regards

Jim R.

[MikeyD]

To Rexford:

Was that the same issue of AFV News where that Duplessis guy also did the glowing review of the brand-new "Combat Mission" game? I hear he also lurks this chat site and refers to himself in the 3rd person (ahem).

As to HC smoke accuracy, the round was light, slow, and flat-nosed but one tank commader claimed to hit a Panther under the gun mantlet in one show at 500m (or was that yards?). Sounds surprisingly accurate all things considered!

[rexford]

Based on a trajectory equation and data for U.S. HC and WP smoke, the following first shot hit probabilities were calculated against a 2.25m high target (average of 2m and 2.5m target height):

150m, 100% for both rounds

200m, 89 for HC, 95 for WP

250m, 68 for HC, 80 for WP

500m, 17 for HC, 23 for WP

750m, 7 for HC, 10 for WP

1000m, 3 for HC, 5 for WP

1372m, 1 for HC, 2 for WP

1829m, 1 for WP

The above analysis assumes no winds, level ground and range is limited by maximum gun elevation to 1372m for HC smoke and 1829m for white phosphorus. Muzzle velocities assumed to be 850 fps for HC and 925 m/s for white phosphorus (figures derived from Duplessis' article in AFV News).

The hit probabilities have also not been modified for first shot drift and jump, which would primarily impact the longer range attempts where the hit probabilities are low anyway.

The computed hit chances suggest that offensive use of smoke via direct hits would be best attempted at close range if the situation demanded a first shot hit (Tiger or Panther is about to rotate turret onto a Sherman).

One of the benefits of slow moving high trajectory rounds (like U.S. smoke, which appear to be fired at under 950 fps) is that the shells do not have a lengthy ground scatter pattern due to vertical dispersion. So smoke rounds can be accurately and effectively "walked" onto a target vicinity if one has the time (and nerves) to change range settings and correct for fall of shot while an enemy may be trying to stop you.

Due to the high trajectory, the chance of hitting vertical targets at longer ranges would be limited, which will be the next computations we will carry out.

The figures for first shot accuracy with smoke rounds are based on an average range estimation error of about 20% that varies from 0% to 60% according to a bell shaped distribution curve.

Based on past e-mails with Conall, 100% accuracy may only be attainable by relatively few gunners and crews due to the effects of stress, fatigue and sloppy aim. When 88L71 misses with Jagdpanthers occur at 500m against fully exposed vehicles, it is not due to bad range estimation errors but totally incorrect aim (uses wrong range line on scope, fails to put cross hairs on target, etc.).

Conall has recommended in the past that all computed hit probabilities be multiplied by a given factor that considers actual combat reactions instead of mechanical, robot like performance:

90% for elite crews

85% for vet

80% for experienced

75% for regular

65% for green

50% for militia

might be assumed for wargaming and approximate research analysis purposes.

Smoke shell accuracy would, of course, be increased on follow-up shots or if previous hit attempts with armor piercing or high explosive shell had hit the target, which identifies the correct range to use. However, since AP, APCBC and HE rounds would have flatter trajectories than smoke, the flatter trajectory ammo would be able to hit with small range estimation errors which would result in misses with smoke.

For example, a 550m range estimation against a target at 500m with 75L40 APCBC puts the round 0.35m over the intended aim point (usually the center of observed target mass). If white phosphorus or HC smoke is aimed at 550m against a target at 500m, the round goes 1.91m over the target center for a miss.

To hit a target on the fly at 1000 yards with smoke takes a very close range estimation error or a bit of luck (which is sometimes better than skill).

P.S. If white phosphorus is fired at a greater muzzle velocity than 925 fps than the relative accuracy would be higher, and possible corrections to the velocity I used would be appreciated.

[rexford]

We note that Duplessis' article is posted on the Saumur Intranets web site at:

http://musee-des-blindes.intranets.com/r.asp?a=5&id=13532

Log on as a visitor and the site will take you to the article.

Otherwise, Rexford notes that the article is in Volume 35, No. 3, if he copied the numbers correctly, which knowing him well, I think he got correct.