Military Bridging and Gap Crossing


[nextpage title=”Introduction”]

Introduction and Sources

The two fundamental roles of the military engineer are mobility and counter mobility.

Any military commander will always strive for freedom of movement and the opposing commander will equally strive to deny that freedom.

Obstacles might be natural or man-made.

Breaching those gaps to provide the friendly force with that essential mobility and freedom of movement is as old as warfare but as speeds of movement increased, the geographic span of operations equally enlarged and the increasing weight of the machinery of war since the turn of the century military bridging has had to rapidly evolve; faster to deploy, longer and greater load bearing are constant drivers of innovation and ingenuity.

In understanding the background we need to look at a few underlying issues that govern the subject.

What is different between a military and civilian bridge?

The main difference is the speed of construction, commanders do not want to wait for bridges that will last a century to be built; time is always precious. So it speed that fundamentally governs the design and operation of military bridging. Detailed site preparations and surveys are unlikely to be possible; the military engineer must carry out a short survey and simply get on with it.

There are always exceptions of course; a number of WWII Bailey bridges are still in regular use today and the military bridges constructed by Roman engineers would hardly be characterised as flimsy rush jobs!

Although they go hand in hand and must be mastered by military engineers, mobility and counter mobility are fundamentally different. For mobility to be maintained; roads, bridges and railways must be constructed or those that are already there and damaged by deliberate actions or natural events must be repaired. Counter mobility seeks to deny mobility to enemy forces by destroying that infrastructure, laying mines or demolishing bridges for example.

Military bridging is a broad term and can be broken down into a number of equipment sub categories;

Non Equipment Bridging; sometimes called expedient bridging or construction bridging it generally uses locally available materials such as timber, stone or steel beams to create the bridge. Despite the full range of equipment and assault bridging equipment now available this is a core Sapper skill and still taught today.

Equipment Bridging; this uses specially designed and manufactured equipment, the Bailey Bridge is a good example of equipment bridging. The category can be subdivided into floating and dry gap equipment although there is often commonality between the two. Recent terminology describes these as wet or dry support bridges although terminology does evolve.

Assault Bridging; a relatively new term that describes specialist equipment bridging equipment used in the direct fire zone, more often than not supporting armoured vehicles in the assault phase. Infantry bridges are somewhat the odd one out but no less important and possibly considered to be an assault bridge.

These are joined by three terms that define how and where they are used;

Close support Bridging (CSB) assets are mechanically launched bridges that enable gap crossing in the direct fire combat zone with crews protected by armour.

General Support Bridging (GSB) and Logistic Support Bridging (LSB) are a mix of mechanically and hand launched equipment with no armour protection and generally used in different locations or phases of an operation. Logistic Support Bridging usually has greater spans and load bearing capacity, used on lines of communication to provide new, replacement or greater capacity bridges.

Factors influencing the design of military bridging equipment include;

Cost and Ease of Production; if a bridge is to be available at the point of need it must be cheap enough for the Army to purchase. If a bridge is so complex and difficult to produce it is likely to be relatively expensive and therefore less likely to be purchased. Ease of manufacture is a fundamental consideration for bridge design.

Reliability and Maintainability; Equipment bridging components are used repeatedly for training and operations most likely over a period of several years. The equipment must be reliable, have predictable wear patterns and where possible, fail in a safe or at least ‘visible beforehand’ condition. Minimising maintenance requirements will also reduce the through life costs of bridging equipment.

Flexibility; if a bridge can be used for differing gap types and conditions there will be obvious training and logistic commonality benefits. Instead of carrying specific bridge types for specific gaps the deployed force can meet the demands of the engineer with a reduced equipment stock holding. A good example of this ‘Lego like’ approach is the Bailey bridge that was used for all manner of bridge types.

Speed of Installation; The users of a bridge will usually be impatient for it to be available, armoured vehicles or men and material queuing up waiting for a bridge to be opened is never a good thing so the ability to build a bridge at speed and recover it with equal rapidity is a major success factor.

Resistance to Environmental Factors; military bridges will be used in all climates and must be able to be built, maintained and recovered in ice, rain or desert conditions and resistance to CBRN agents is a recent addition to the list of conditions the bridge must withstand.

Transportability; equipment bridges will need to be transported to bridge site. The components will have to conform to the available or intended means of transport. The generally manifests itself as transport by truck but there are specialist air portable bridges that must fit within the lift parameters of support helicopters like the Chinook.

Load Bearing; finally, a bridge must be able to traffic whatever equipment is intended to use it. An assault bridge must be capable of bearing a main battle tank, a logistic support bridge a heavy recovery vehicle towing a heavy equipment transporter towing a trailer that is carrying a main battle tank. Reflecting the most likely equipment to cross an air portable, they generally sacrifice load bearing capacity for portability.

One of the great unsung success stories of British military endeavour is that of gap crossing, or perhaps more commonly known as military bridging.

The British Corps of Royal Engineers, its forebears and associated civilian engineers and organisations have been at the forefront of military engineering for many hundreds of years. The iconic Bailey Bridge is of course a symbol of this but before and since have been a number of equally revolutionary designs and techniques that have advanced the art, and it is an art.

We might argue the same for many areas of military endeavor but bridging or gap crossing is a true stand out and yet little exists online to celebrate this.

This is the story of British Military Bridging.


Rather than presenting this as a strict chronological history this Think Defence Project Page is structured to reflect the evolution of military bridging as book-ended by bridge types and methods, timelines will therefore overlap.

Content has liberal hotlinks that readers can use for additional reading and in some cases these links will have provided inspiration and factual information for the main post, acknowledgement is assumed in these cases.

In addition, a number of primary sources have been used.

Although the internet is a superb research tool (even Wikipedia) there is no substitute for an old fashioned cracking read, in this case, One More River to Cross written by JH Joiner. Don’t go to Amazon, if you are at all interested in this subject and want to know more beyond this page pop over to the Sapper Shop to buy the book and visit the RE Museum in Brompton.

[/nextpage] [nextpage title=”Early Days” ]

The Emergence of the the Military Bridge

[/nextpage] [nextpage title=”Load Classification” ]

Load Classification

[/nextpage] [nextpage title=”Non Equipment Bridging” ]

Non Equipment Bridging

[/nextpage] [nextpage title=”Early Pontoon Bridges” ]

Early Pontoon Bridges

[nextpage title=”Fascines” ] [/nextpage]


[/nextpage] [nextpage title=”Early Assault Bridging” ]

Early Assault Bridging

[/nextpage] [nextpage title=”The Inglis Bridges” ]

The Inglis Bridges

[/nextpage] [nextpage title=”The Hopkins Bridges” ]

The Hopkins Bridges

[/nextpage] [nextpage title=”Large Box Girder Bridge” ]

Large Box Girder Bridge

[/nextpage] [nextpage title=”Small Box Girder Bridge” ]

Small Box Girder Bridge

[/nextpage] [nextpage title=”Folding Boat Equipment” ]

Folding Boat Equipment

[/nextpage] [nextpage title=”Callender Hamilton Bridge” ]

Callender Hamilton Bridge

[/nextpage] [nextpage title=”Scissor and Tank Assault Bridges” ]

Scissor and Tank Assault Bridges

[/nextpage] [nextpage title=”The Bailey Bridge” ]

The Bailey Bridge

[/nextpage] [nextpage title=”Railway Bridges” ]

Railway Bridges

[/nextpage] [nextpage title=”Rafts and Ferries” ]

Rafts and Ferries

[/nextpage] [nextpage title=”Air Portable Bridges” ]

Air Portable Bridges

[/nextpage] [nextpage title=”The Heavy Girder Bridge” ]

The Heavy Girder Bridge

[/nextpage] [nextpage title=”The Medium Girder Bridge” ]

The Medium Girder Bridge

[/nextpage] [nextpage title=”Trackway and Matting” ]

Trackway and Matting

[/nextpage] [nextpage title=”Close Support Bridging System” ]

The Close Support Bridging System

[/nextpage] [nextpage title=”General Support Bridging System” ]

The General Support Bridging System

[/nextpage] [nextpage title=”Logistic Support Bridging System” ]

The Logistic Support Bridge

[/nextpage] [nextpage title=”The Future” ]

The Future

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