Since I did not want to hijack/obscure the SITREP thread, I'm posting details and findings here, to put it up for discussion:
Were gun batteries able to put enough ad hoc smoke on the ground to obscure ... ?
The U.S. War Department publication 'Tactical and Technical Trends' No. 6 August 27 1942 said:PART ONE
Research on German use of smoke as a weapon has produced considerable information on the organization of German smoke units and the large-scale use of smoke in tactical roles.
The idea that climatic conditions in the Middle East made the use of smoke impracticable has been proved by experience to be incorrect. Conditions will vary, but it will frequently be possible to use smoke effectively.
German Smoke-Producing Units (Nebelwerferabteilungen)
Six of these units have thus far been identified in the German Army. It is possible that eventually each Corps will include a smoke-producing unit. These have been identified in regimental chemical headquarters but only as administrative, non-operational headquarters.
Engineer Units. These are believed to be equipped with smoke projectors manned by sections of two to three men. The scale of equipment is not known.
... [ ] Army and corps commanders allot smoke troops, equipment, and ammunition to subordinate formations for large-scale screening operations. The divisional commander usually decides on the use of smoke, and its exploitation by artillery fire and troop movements. In employing smoke heavy concentrations are usually sought. The following uses are quoted:
(1) Concealment of forward movements, and initiation of surprise attacks.
(2) Reduction of casualties.
(3) Assistance in taking open ground
(4) Covering river crossings.
(5) Blinding enemy positions and observation posts.
(6) Economy of ammunition, and reducing artillery's task.
(7) To some extent replacement of covering fire.
(8) Assistance to the main effort of the attack.
(9) Concealment of weakness in the secondary attack or of gaps in the attacking forces.
(10) Protection of flanks.
(1) Blinding enemy observation posts.
(2) Concealing activities in the main line of resistance.
(3) Concealing troop movements to prevent observation from ground and air.
Throughout German teaching it is emphasized that smoke must always be laid on the enemy and not on friendly troops. The normal use of smoke to assist daylight withdrawal and to blind the enemy is also mentioned.
An interesting use of smoke is found in the suggestion that screens might be put down purely as a deceptive measure to mislead the enemy as to intentions.
The following principles are laid down for German troops when fighting in smoke:
(1) Smoke impedes defense rather than attack.
(2) Route-finding by compass is essential.
(3) Units should be guided through pre-assigned sectors.
(4) Close combat is decisive.
(5) Careful preparation of fire plans is essential in defense.
(6) Particular points of danger should be protected by units armed with bayonet.
(7) Counterattack should take place, as a rule, after the dissipation of a smoke screen.
(8) Gas masks should be worn until it is definitely known that no chemical warfare gas is mixed with the smoke.
It should be noted that no distinction is made between smoke laid down by enemy or friendly troops.
Instructions have been given for the handling of "smoke acid", which has been described as a mixture of chlorosulphonic acid and sulphur trioxide.
... [ ] ...
(c) The Improvised Smoke Projector. This weapon can project the Smoke Candle 34, up to a range of 500 meters (550 yards). It consists of a steel barrel, 94 mm. (3.7 in.) in diameter, 4 mm. (.157 in.) thick, and 600 mm. (23.62 in.) long. The base plate, 200 mm. (7.87 in.) square and 10 mm. (.39 in.) thick, is welded on. A bipod is attached to the barrel by a ring just behind the muzzle. The best results are produced when using an elevation of about 45 degrees, which gives the maximum range for any of the three charges which may be used. These charges are made up of 25 (.54 pound), 50 (1.08 pounds), and 100 (2.16 pounds) grams, respectively, of propellant explosive in small packets of gauze or cellophane. The method of operation is to insert the charge into the barrel and drop in the smoke candle with the safety pin already withdrawn; this ignites the charge and the candle is projected to a distance depending on the charge, the angle of projection, and the wind. The rate of fire is 3 r.p.m. The average ranges attainable are:
With 25 grams propellant 100 meters (110 yards)
With 50 grams propellant 200 meters (220 yards)
With 100 grams propellant 500 meters (550 yards)
The most effective use of this projector is said to be the engagement of entrenchments and dugouts, and as a covering for river crossings. It can be mounted in the assault boat issued to engineer units.
(d) Tank-Mounted Smoke Candle Rack. All German tanks carry, projecting from their rear, a rack on which 5 smoke candles are held. These candles cannot be projected but are dropped from inside the fighting compartment. No definite evidence on their effect has yet been received.
A captured German General Order dated April 1942, mentions the fact that the smoke-candle discharger apparatus fitted to tanks has not proved successful and that a new type is being designed.
(e) Smoke-Producing Agents. For smoke candles and grenades a solid substance composed of zinc powder and hexachlorethane is used. This is quite normal. The shell is said to contain sulphur trioxide, but a 75-mm. shell which has actually been examined was found to contain oleum. Certain types of smoke generators sometimes use chlorosulphonic acid in conjunction with oleum or sulphur trioxide. In this connection, there have been two recent reports from the Western Desert of a thick cloud over 100 yards deep having the appearance of chlorine, but not in fact composed of this gas. The cloud was said to be used tactically on both occasions, and to be heavier and more intense than clouds normally caused by smoke-producing apparatus. In appearance, however, clouds produced by chlorosulphonic acid could be mistaken for chlorine.
The average height of a normal smoke screen is said to be 10 to 15 meters (32 to 49 feet), and the width 25 to 30 meters (82 to 98 feet). The length is:
Smoke Candles and Sprays 200 - 300 meters (220 - 330 yards)
Smoke Shell 100 meters (110 yards)
Smoke Hand Grenades 30 - 50 meters (33 - 55 yards)
The report from 1942 is very interesting. It shows what information Allied intel branches had gathered, and also shows where German deception had at least partially worked:
"German Smoke-Producing Units (Nebelwerferabteilungen)
Six of these units have thus far been identified in the German Army. It is possible that eventually each Corps will include a smoke-producing unit. These have been identified in regimental chemical headquarters but only as administrative, non-operational headquarters."
This reference shows that the Allies actually bought the pseudo purpose of the Nebelwerfer ("smoke throwers") units, as well as the whole Nebeltruppen (smoke troops) branch, which had already transformed into rocket artillery units. The US War Department's summary actually manages to pinpoint some of the details of the organizational structure of the (pre-war) Nebeltruppen (smoke troops), as it states that they were "regimental chemical headquarters", but then goes on and falsely identifies them as just administrative, non-operational HQs, where it then does not manage to reveal the general structure and the pre-war purpose of the Nebeltruppen as chemical warfare sections responsible for handling/firing chemical weapons and for decontamination. The major shift towards a rocket artillery role with the Nebelwerfer 41, and the fact that every unit in the German Army had a chemical appointee, was not gathered by the Allies either, at that point, obviously.
There is another misconception: The report quotes a captured General order stating that the smoke cups on tanks were not successful. This is not entirely true. The external smoke cups (mounted on the side of the turret) were prone to damage caused by shrapnels and even rifle rounds, where then the electrical trigger could fail. Also, when empty, a crew member had to get out and reload the cups. While failed or damaged cups were not mass phenomenons, it was still disturbing for the tank crews, as smoke cup failures made tactical retreats somewhat more difficult. The new design envisaged the smoke rounds to be fired from inside, through a dedicated smoke cup hatch, which had a kind of flare gun attached to it on the inside (firing the same smokerounds as the external cups, iirc). The gun could be removed. At least the King Tiger received such a hatch.
The report is from 1942, so - of course - Western Allies were less exposed to and less familiar with certain German assets or tactics than the Russians.