Battlefront:WWII Some Facts about Bridging operations
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Sources:
Closing with the Enemy : Michael D. Doubler Chapter 6
First Across The Rhine: Col. David Pergrin
Doubler cites the War Department Field Manual 5-6 which defined the U.S. Army's doctrine for river crossings
and then shows how things worked in practice.
Pergrin relates his personal experiences as commander of the 291st Engineer Combat Battalion.
To start the assault, a river crossing was made with M2 Assault boats, each of which could carry
and infantry squad + their equipment. 17 such boats were to carry a full company. On some of the
larger rivers, landing craft and amphibious vehicles were also used.
Before the bridges were in place, heavy equipment could be ferried across using "infantry support
rafts" which were 6 boats lashed together with a plywood top. These could carry up to a fully loaded
2 1/2 ton truck, as well as such items as supplies and anti-tank guns.
The U.S. Army used four basic types of bridges, only 3 of which were likely to be placed in a combat
zone.
The lightest bridge was an infantry foot bridge, which was a walkway up to 400 feet long laid over
light pontoons.
A heavier pontoon bridge was the M2 treadway bridge, which had up to a 40ton capacity. This could
be of any length, and was what was used over major river obstacles such as the Rhine and Moselle. Doctrine
stated that it would take 5 1/2 hours to place a 362 foot section of M2 treadway during daylight and 7 1/2
hours at night. Pergrin says that in practise 50ft/hour of treadway construction was expected, which is
a little slower than the speed specified by doctrine.
In practice, it often took longer because of enemy action and the elements.
Two 1000 foot bridges were laid across the Rhine in the face of heavy enemy opposition in about 30 hours each.
Over the Danube it took 12 hours to place a 450ft treadway over a muddy approach under fire.
In the crossings of the Rhine in the North, a 952ft treadway was placed in 10 hours, which was
better than the expected speed. This higher speed was attained by building multi-float sections
on the friendly bank and then hooking them together once the construction began, rather than by adding
on one float at a time.
Pergrin also says that it was very difficult for artillery to damage the parts of treadway
bridges that had been placed because the water tended to dissipate the effects of all but a direct
or very near hit. The approaches were more vulnerable. The Rhine bridges were placed
under the heaviest fire, but even though the Germans managed to knock many of individual floats,
they never succeeded in destroying the bridges.
The British prefabricated Bailey bridge was often used. It also had a 40ton capacity, and a length
of up to 180 feet. It was known for its speed of construction and did not use pontoons. According to doctrine,
a 90 foot section of Bailey bridge could be placed in 4 1/2 to 5 hours.
Bailey Bridge construction in practise (Pergrin)
After the Bulge, the engineers had to construct a 180 foot span over the 80ft deep cut
at Lanzerath. This was done under fire starting 1FEB and took 40 hours to complete.
At Blens, a 130 foot triple span took about 15 hours.
At Heimbach, a 110 foot span took 18.5 hours to complete.
With no opposition, Bailey bridges were easier to place, and experienced engineer units
often approached or exceeded the speed assumed by doctrine:
The 75ft wide gap in the Schwammeauel Dam was bridged in 7 hours 45 minutes.
After the breakout from the Remagen bridgehead, 3 engineer companies placed 14 Bailey bridges
in 37 hours.
At Markhausen, a 90ft Bailey was placed in 3 3/4 hours.
At Megan, a 70ft Bailey was placed in 3 hours.
A 80ft Bailey was placed on a gap in the autobahn in 2 1/2 hours.
A 120 ft triple span was paced at Grevenbruck in 17 hours
An 80 ft span was placed at Fürth in 3 1/2 hours
Behind the front lines, engineers spent much of their time constructing timber trestle bridges, which
could carry heavy loads at high speeds and were essentially permanent structures. Timber trestle bridges should
appear in our scenarios primarily as targets for demolition.
As can be seen from the times above, most bridging actions are beyond the tactical scope of Battlefront:WWII, where the usual battle is limited to 2 or 3 hours duration. However, smaller river crossings are possible, and it is possible to construct a scenario based on small crossings or the completion of the final one or two stands of a large crossing. Pergrin cites a battle over the Vire river and Vire-et-Taute canal in Normandy where a 20 foot infantry bridge was placed in 35 minutes while under enemy fire and a single section of treadway was placed in 20 minutes.