Bridges in War

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The topic of bridges in war may be divided into two categories. Firstly we may consider what happens to existing bridges, and secondly we may look at the bridges that are constructed specifically by and for military organizations.  For the second subject please click here.

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Bridges in time of war

The actions of military forces on bridges may be categorized as follows, in a conflict between nations A and B.

Location of bridges

     Bridges in territory held by A

          Bridges in A's own lands

          Bridges in B's land currently occupied by A

          Bridges in neutral nation currently occupied by A

     Bridges in territory held by B

          Bridges in B's own lands

          Bridges in A's land currently occupied by B

          Bridges in neutral nation currently occupied by B

     Bridges in neutral territory C, currently unoccupied by A or B

Actions to be taken will depend not only on the considerations listed, but on the course of the conflict, the purposes of each side, and what they think may happen next.

For example, decisions about bridges in neutral territory C which is not currently held by either combatant will depend on real or imagined intentions.  If A intends to pass through C as part of its strategy against B, it will not want to destroy any bridges in C, but if it fears that B will use C against A, then it may well seek to destroy strategic targets.

As to the other categories, decisions will depend on whether A and B are advancing, holding, or retreating.  In any given situations, the decision might be to defend a bridge or to attack it, whether it be in one's own land or elsewhere.

As an example, as the German forces retreated northward through Italy during WWII, they naturally wanted to destroy bridges to deny the advancing forces, but in one case they were persuaded to leave a bridge unscathed.  This was the Ponte Vecchio in Florence.

A recent example of a bridge destroyed in war is the bridge at Mostar - Stari Most - which has just been rebuilt.  Some of the effects of the destruction are described in "Bridge: the architecture of connection" by Lucy Blakstad [pub Birkhauser (Architectural) ISBN 3764366435.]

As we have seen, there are so many possible military situations that they will not be discussed here, and in any case the subject requires professional knowledge.

There are of course, effects of bridge destruction that are not intrinsically military.  Although the effects of destruction on the local population - loss of mobility, reduction in trade, etc - may be considered to be military objectives, there may be side effects in other areas.  The destruction of large bridges over a wide navigable river may deny commercial shipping the use of the channel until the wrecked structures are removed.  That may not happen until the conflict is quite far into the past.

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Military Bridges

Far back into history, armies have needed to cross water.  The importance of these crossings is reflected in the phrases "burning your boats" and "burning your bridges".  Do you know of any instances where either of these actions was deliberately done?

The essence of a military bridge is that its parts must be portable using available transport equipment, such as trucks, tanks and helicopters.

Some specialist tracked vehicles carry folding bridge decks, which can be unfolded in front of the vehicle, cantilevering out over the gap, until they rest on the other side, at which point the deck is locked at its mid-point, becoming a beam.  Such a bridge can be strong enough to bear large trucks and tanks.

A different approach is to assemble a bridge from a set of pre-fabricated standard parts which can be assembled in different configurations.  The Bailey bridge is a well-known example.  The other Mostar bridge.  See also Acrow bridge and Mabey-Johnson bridge, the last being a form of pontoon bridge.  See also A Canton and Co and Mabey and Johnson.

The pontoon bridge is an ancient form of construction, which can be based on boats or on purpose built pontoons, which are essentially piers that float instead of resting on the bottom of the channel.  Segmental decks can be laid on the pontoons, and hinged together to form a strong deck.  If the pontoons are close enough together, the spans can be simple wooden beams.  Some ancient boat and ship bridges were like that.  Modern techniques allow for fewer pontoons and longer spans.

Military bridges entered a new age with the American Civil War, because of the need to carry railroads.  In modern times, heavy tanks and artillery pieces have to be carried.

          Links about military crossings

          Bridges for Darius and Xerxes over the Bosporus and Hellespont

          Rhine bridge by Julius Caesar's engineers

          Woodbury's bridge

          Fort Laramie bridge

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