The following information concerns types of construction of concrete walls
and other antitank obstacles in Holland, Belgium and France. Further details on
this subject are contained in the publication, German Coastal Defences, issued as
Special Series No. 15, 15 June 1943 by the Military Intelligence Division, War
Walls are used to block streets and roads in coastal towns, as obstructions
on approaches to key points, and on the outskirts of towns generally. Road blocks
of this type, erected in line with the front elevation of existing buildings, will often
form a continuous obstacle along the entire sea front of the town.
Details of the steel reinforcement of such walls have not been learned but
it is suspected that it is very light and in some cases does not exist at all. Hooked
bars often project from the top of the wall and may be used to support wire. To
increase the effectiveness of walls as obstacles, ditches are often excavated or
pits are dug and covered with planks, road metal or netting.
In areas where large quantities of stone are readily available from quarries,
road blocks are often constructed of stone and not concrete.
V-shaped walls may be found across beach exits, especially on open beaches
outside of towns. Gun emplacements or small pill boxes may be found at the point
of the V, which is to the front--towards the sea.
Concrete walls have a minimum thickness of 6 feet but probably average
8 to 11 feet in thickness. Height varies from 6 feet to 8 feet, 6 inches.
When walls are gapped, the gap is usually sufficient for one vehicle to pass
at a time. In one type the walls are built opposite one another from each side of
the road, the gap being closed at will by girders, rails or gates which fit into
sockets precast in the wall ends.
Another obstacle that may be encountered in the coastal districts of northwest
Europe is a staggered type of double road block consisting essentially of a
pair of walls or barricades built one behind the other and projecting from opposite
sides of the road for a distance of one-half to two-thirds of the width of the road.
These double road blocks may be constructed of masonry or concrete, or
they may be earth-filled timber barricades. Horizontal and vertical members of
timber barricades are described as 10-12-inch diameter pine logs, the vertical
members driven deep into the ground. The walls are strengthened by diagonal
bracing. Apart from the presence of a passage through them, these barricades
would form an effective obstacle against a frontal assault by medium tanks, though
a heavy tank may cross and probably demolish them. Where these barricades are
constructed in concrete it is fairly certain that they are not less than 6 feet
thick. The average height has not been reported.
Concrete obstacles known as "Dragon's Teeth" are also used to block
streets, exits from quays, and well defined beach exits, particularly where the
level of the beach approximates the level of any road or track. This type of obstacle
often consists of three or four staggered rows, 6 to 8 feet apart, the distance between
the teeth in each row being 6 to 8 feet. The "Dragon's Teeth" probably average
2 feet, 8 inches to 3 feet in height. It is possible that the teeth are connected at their
bases, from front to rear, by concrete beams to prevent overturning. No information
is available of any steel reinforcements in the teeth.
Concrete cubes are used in the same way as "Dragon's Teeth" and are
also found across hollows in dunes which might provide exits for vehicles. Cubes
are used in rows, not always staggered. In dune country they are generally on a
forward slope, near a crest. Where the pillars are rectangular, they measure
about 3 feet on each side by 4 feet in height. Other obstacles of this type are about
4 by 4 feet in dimensions.
In addition to concrete and stone, steel is often used in the construction of
beach and road obstacles.
Steel tetrahedra, pyramid-like, are made of steel rails or L-sections. They
consist of 3 or 4 lengths of steel in the form of a cone, with the ends embedded in
concrete and bolted at the top. When obstacles are made of L-sections, the upper
ends appear to be specially cut and are welded together at the apex. There are
two types, one which is 3 feet, 3 inches high with the ends bolted or welded, and
the other type 4 feet, 6 inches high, bolted 3 feet, 3 inches above ground level with
the ends projecting above the join.
Steel rails are occasionally placed vertically in 2 or 3 rows to form blocks
across streets or well defined exits on open beaches. The rails project about 4 feet
above ground level and are embedded in concrete.