What follows is believed to be the official views of the German Army on
the possibilities and limitations of ice in so far as it affects the passage of
military traffic over water obstacles. However, while the views expressed are
presumed to embody the lessons learned during the Russo-Finnish war
of 1939-40, they do not embody the experience gained by the
Germans during the Russian campaigns.
* * *
In general, freezing conditions lessen the value of water as an obstacle
and make the terrain more passable; this will tend to weaken the defense and
strengthen the attack. On the other hand, ice floes and thin ice considerably
increase the difficulty of crossings and necessitate special measures.
a. Roads Across Ice
The following are the loads which can be supported by sheets of solid ice
of various thicknesses, lying on water:
|1 1/2 in . . . . . . . . .||Single infantrymen|
|2 in . . . . . . . . . . .||Infantry in open order|
|4 in . . . . . . . . . . .||Single horses|
|6 in . . . . . . . . . . .||Infantry and horsed cavalry in column of march, with light motor transport|
|8 in . . . . . . . . . . .||Light artillery up to 2 1/2 tons, horse-drawn, and 4-ton wheeled vehicles, maximum axle load 2.7 tons, minimum interval 65 feet|
|1 ft . . . . . . . . . . .||10-ton wheeled vehicles, maximum axle load 7 tons, minimum interval 65 feet|
|1 ft 2 in . . . . . . . .||20-ton wheeled vehicles, minimum interval 100 feet|
Experiments have shown that a sheet of ice 10 inches thick will carry
tracked vehicles up to 16 tons at an interval of 165 feet, moving
at a speed of not more than 2 1/2 mph, provided that track slip
Ice will carry heavier loads over still water than over streams and rivers. The
thickness of the ice may vary over the same stretch of water; if, for instance, warm
springs are present the ice will tend to be thinner, or if the river bed is locally
swampy it will tend to be thicker or even frozen solid through to the river bed. A
layer of snow on the ice diminishes its strength, since the warmer water from the
bottom does not cool on rising as readily as in the absence of snow, which tends to
insulate the ice from the cold atmosphere. Warm weather (thaw) diminishes the carrying
capacity of ice very rapidly, even when the thickness of the ice remains the same
since the ice becomes somewhat porous. The thickness of ice should be determined
by boring; at the same time it should be ascertained whether the ice is lying on
water. In doubtful cases loading tests should be carried out. Holes and open
patches (found mostly near the banks) should be treated with special care. Changes
in water level, particularly associated with dams, must be carefully observed.
To prepare it for traffic, ice should be covered with gravel or sand. On both
sides of the roadway over the ice a strip at least 16 feet wide should be
kept free of snow, to permit observation of any cracks in the ice. Single cracks
running transversely across the roadway do not appreciably diminish its carrying
capacity, and can be closed in cold weather by pouring water on them. Heavy cracks
running parallel to the track indicate that the carrying capacity of the ice
is becoming exhausted.
In sufficiently cold weather, ice can be strengthened or reinforced by the
addition of further ice layers. This can be done by the following methods:
(1) Laying and watering of sawn-out blocks of ice;
(2) Addition of water, using low snow dams, the water being allowed to freeze;
(3) Addition of straw, twigs, or reeds which are watered and allowed to freeze.
Strengthening of ice in the above manner can only be carried out if the
ice is at least 1 inch thick. The carrying capacity of reinforced ice increases
approximately according to the figures already given, but the capacity of the
additional "artificial" layer should, in actual practice, be calculated as only half
that of natural ice. In strengthening ice the width of the strengthened belt should
be at least 2 1/2 times that of the roadway itself. After strengthening, small
holes should be drilled in the ice in the neighborhood of the roadway; these will
allow the water to seep through and improve the equilibrium of the ice-sheet. The
roadway must be carefully marked off, and if in constant use, should be provided
with a light surfacing.
Track for the passage of vehicles may be constructed of chess or other
planking. Vehicles will normally run at very low speeds on two treadways. Joints
of these treadways must be staggered to prevent simultaneous impact on
both joints. The load may be spread by timbers placed under the treadway. If
boards are placed as cross ties, they should be close enough together to insure
that the heaviest loads do not bend the treadway sufficiently to strike the ice.
If ice is artificially strengthened, test loading must be carried out in each
instance. The carrying capacity of ice may be diminished by excessively heavy
For assault infantry crossings, the light assault bridge using planks
instead of floats is suitable.
b. Use of Boats in the Presence of Ice
Assault boats, strengthened by thin metal sheeting along the water line, can
be used as ice breakers, to cross water covered with ice up to an inch in
It is possible to negotiate streams filled with ice floes if the current is
not too rapid and the floes are of sufficient size and thickness. Pontons must be
protected by round timbers or planks secured to the sides with ropes. Floes
must be kept off by men standing in the bow and using short boathooks. Large
pneumatic boats can be protected in the same way.
c. Ice Bridges
With weather continuously freezing, ice bridges may be constructed to
cross short stretches of open water or thin ice. A large block of ice, at least
thirteen feet wide, as thick as practicable and several feet longer than the span
of water or thin ice, is cut and moved to bridge the gap. This ice bridge may be
strengthened according to the methods previously described.
In slowly moving water, it may be convenient to cut the block of ice adjacent to
the bridge site and parallel to the bank (see sketch below). After removing the
other ice on a ninety-degree arc, it is possible to pivot the block of ice about
point A (see sketch) and use the current to swing it into place. Notches
cut in the ice on the two sides of the bridge site will hold the block in place.
d. Bridging in the Presence of Ice
In general, ice bridges should be replaced as soon as possible by regular
bridges. Fixed supports are preferable to floating supports for this purpose. Long
spans diminish the danger to the bridge on the breaking up of the ice. Piles
should be shod with metal, and some form of ice breaker should be used. Floating
supports must be capable of submerging when the bridge is loaded, and should be
kept free from ice. Light boats and pontons will be crushed by thick
ice, even in still water. For streams where the flow of ice is heavy and those in
which the danger of break-up is great, bridges with floating supports cannot be
Construction of bridges in the presence of ice floes is difficult, and unforeseen
incidents are of such frequent occurrence that definite figures for the
time required cannot be laid down. Improvised bridges on floating supports
can only be erected when floes are small and the density not too great; under
these conditions the floes must be continually pushed away from the supports
and allowed to pass under the finished bridge. With larger floes a bridge can
only be built if the ice can be broken up at a sufficient distance upstream.
Anchor cables are apt to wear through after a short time; they should
accordingly be preserved by being enclosed in three-sided wooden casings, about
10 feet in length, which keep the lines from direct contact with drifting
ice. Wire ropes are especially suitable for use as anchor cables under these
conditions. Rafts used for pile-driving must be protected from drift-ice by
metal boats or floats anchored upstream.
When working on ice, it may be necessary to rope pairs or groups of
men together for safety.
A party on guard upstream should be amply provided with explosives
and fuzes for the destruction of ice.