Air raids on military targets in Germany and in the occupied countries
have compelled the Germans to intensify defensive measures through the use of
area smoke screens (see Tactical
and Technical Trends No. 24, p. 8 for previous
reference to this subject). Such screens have been used to confuse our bombers
by obscuring their targets and to interfere with our photographic reconnaissance.
Screens used early in the war showed progressive development but were,
in many cases, quite inadequate to conceal the places and installations which they
were designed to protect. Small numbers of points of smoke emission, far apart,
were characteristic except at Brest and Kiel where, over a period of time, screens
of constantly increasing effectiveness were built up. Large, dense screens over
Berlin were also noted in early 1941. It is probable that German experience at
these places has been useful in the planning of screens for other cities, both inland
and on the coasts. It is noteworthy that the smoke producers for most of the earlier
screens were placed in close proximity to the targets.
Later screens show a greater similarity in technique, although there are
still considerable divergences, some of which may depend on the relative importance
placed on the defense of one point as against another.
Features of current activities in smoke screen defense are as follows:
(1) Daylight Screens
Coincident, no doubt, with the daylight raids of the U.S. Air Force, the
Germans have been making much greater use of daylight screens than they did
before January of this year. The technique appears to be the same as for night
(2) Placement of Smoke Producers
An average spacing of 75 to 100 yards between smoke producers is the
current practice, according to latest information. More closely placed producers
have, however, been seen in several places, notably Berlin, Warnemunde, Gdynia
and Foetten Fjord. In no place does it appear that any system of equal spacing is
rigidly used. The different smoke-producing capacities of various types of
equipment used and the directions of prevailing winds are undoubtedly controlling factors.
In some cases the smoke producers are now being located at considerable
distances from the targets. This is done to conceal landmarks in the vicinity
which would enable attacking airmen to estimate accurately the position of the
target even when it is covered by a heavy screen.
It is a tribute to the effectiveness of our bombing raids that the enemy
have been driven to the necessity of greatly increasing the size of their screens,
involving more rapid consumption of their supplies of smoke chemicals and the
provision of greatly increased amounts of equipment. At Bremen recently, smoke
ejectors were seen to extend for a distance of 12 miles east and west and 11 miles
north and south.
(3) Subsidiary and Decoy Screens
Other tactics tried for the purpose of protecting vital installations have
included the use of separate subsidiary screens to hide easily identifiable
landmarks, and the use of decoy screens to confuse attackers as to the real location
of their targets. Tactics of this kind are probably more effective at night.
(4) Time for Screen Build-Up
The time required by the Germans to build up an effective screen averages
15 to 20 minutes after the alarm is given.
(5) Number of Smoke Producers Used
The number of smoke generators necessary to produce a good screen
depends on generating capacity. At Emden, 56 generators, spaced from 60 to 110
yards apart, formed a dense layer of smoke extending for 3 1/2 miles; at Brest,
at least 117 generators were used, 70 yards apart on the fortifications, elsewhere
90 to 130 yards apart.
(6) Smoke Producers On Boats
To provide coverage over harbors, smoke producers are placed on moles
and jetties and on small craft, suitably located, as well as on roads around the
towns. At St. Nazaire, 17 barges anchored in the Loire river up-wind from the
city, have served this purpose. Smoke floats may have been dropped off boats
into the waters or harbors to increase the smoke output of spray equipment.
(7) Smoke Producers on Trucks
Smoke producers mounted on trucks have been used to reinforce smoke
screens by moving from place to place according to need as dictated by wind
direction and velocity.
(8) "Dazzle" Effects On Screens
Searchlights have been used in connection with low-lying smoke screens, not
to pick up attacking planes but to cause a dazzle effect when the light is
reflected by the millions of tiny particles of smoke cloud.
(9) Pouring Smoke Liquid On Water
Either experimentally or, more likely, because of a shortage of spraying
equipment, the Germans, on a few occasions, have poured smoke liquid into the
waters of a Norwegian fjord to produce a screen. It was estimated that it took a
half hour before an effective smoke cover could be produced. The liquid used in
this way was not identified but was possibly either titanium tetrachloride or a
chlorsulphonic acid oleum mixture.
(10) Places Where Area Smoke Screens Have Been Used by the Axis
(11) Reported But Not Confirmed Use of Screens
Greiz (nr. Plauen)
*Based on information as compiled by the Office of Chief of Chemical Warfare Service.