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Assault bridging and equipment


The beginnings

The earliest example of an assault bridge is the fascine first identified as being used in Roman times but probably earlier.

A fascine consists of a bound bundle of brushwood. These were carried into battle by the soldiers and thrown into ditches to rapidly make a temporary bridge across which they could pass.

When tanks were first used in First World War (1914-18) it was quickly appreciated that some sort of temporary material was needed to bridge shell craters and other man made obstacles. Giant fascines weighing 1.5 tons were manufactured and carried on top of tanks. When an obstacle was reached the fascine was cut loose and rolled into the gap. The tank could then continue its way forward. The fascine remains in use today, now created using plastic drainage pipes. The humble fascine is probably the single longest serving piece of military bridging equipment.

Fascine mounted on AVRE - 1944
Fascine mounted on AVRE - 1944

Post-First World War developments

Assault bridges are designed to be used primarily in the battlefield under fire. They have a limited span and are pushed or carried into position using an armoured vehicle, usually a specially adapted tank.

Assault bridges have their origins from a small portable bridge designed by William Tritton of William Foster & Company. This company produced a petrol tractor which was used to tow a 15" Howitzer. One of these tractors was modified to carry Tritton's bridge which could be positioned across an 8' gap in about three minutes. The idea was not developed further because of the vulnerability of the tractor and crew to enemy fire. The first purpose designed equipment was a sledge bridge towed behind a tank. This was dragged across the gap but little used in action.

Major Charles Inglis RE, the Corps bridge designer looked at the problem and produced a design for the Canal Lock Bridge which had a 21' span, sufficient to cross a canal lock. This was mounted on the front of a Heavy Mark V Tank and could be lowered like a draw bridge across the gap using a system of chains and 2 A frames. Major (later Lieutenant General Sir) Gifford le Q Martel RE, now heading the Experimental Bridging Establishment (EBE), Royal Engineers suggested that the power of the tank engine should be used to place the bridge hydraulically. This was done and the hydraulically operated jib could also be used as a small crane. Used in conjunction with special 2 ton rollers it could clear mines - a fore runner of the World War II flail tank.

Lt Gen Sir Gifford le Q Martel
Lt Gen Sir Gifford le Q Martel
He commanded the Experimental Bridging Establishment at Christchurch, Dorset, effectively founding the future MEXE.

They were known as Heavy RE tanks and although they were not developed further the idea was resurrected in Second World War (1939-45), when they were referred to as the Armoured Vehicle Royal Engineers (AVRE).

Canal Lock Bridge on Mark V tank
21ft Canal Lock Bridge carried by a heavy Mark V tank - 1920's
(Photo: IWM T18)

The Inglis Assault Bridge was also developed consisting of a standard Inglis Bridge mounted on twin idler tracks [non-powered], designed to be pushed into place by a tank but it was never used in action. This could be pushed across a gap of 70' in about 1 minute.

In 1925 Major HH Bateman RE, who was at that time (the first) Superintendent of the EBE, produced an alternative design to Inglis's Lock Bridge based around the Dragon Artillery Tractor. It was a 30' bridge with a working span of 20'. Consisting of steel joists with no decking, it could be launched from the Dragon. It was only usable by tracked vehicles, a longer span with a light launching nose was later developed.

Another fascinating development was the Stepping Stones bridge. It consisted of a substantial timber framework forming a skeleton box about 4' square and 12' wide. A number of these were joined by rope and could be pulled across a river of up to 4' or 5' depth. The tank would then be driven across the top of the framework which grounded on the river bed. Suffice it to say that tank drivers were not over keen on them, and although consideration was given to 8' square units they did not get beyond the trial stage.

The EBE revisited assault bridges in the late 1930s, and whilst none of the prototypes then developed went into production they were very important. Each used a different launch method which were used in later designs. The methods were:

  • Scissors
  • Up and Over (horizontal launch)
  • Travelling jib

The British were at the leading edge of assault bridge design at the start of the war.

The Dragon Assault Bridge was the subject of a preliminary design by Martel. Subsequent development was done by Lieutenant HAT Jarrett-Kerr RE, who later when a Brigadier was the last military Director of the Military Engineering Experimental Establishment (MEXE), as the EBE became after the War. It was based on the Dragon Artillery Tractor and used the Small Box Girder (SBG) bridge components. Consisting of 2 SBG ramp sections its length was 34' 6". Carried upside down on the Dragon it was launched by the 'up and over' method using a hydraulic ram, a light derrick and winch cable. The bridge was raised to a vertical position with the derrick rising behind it. The winch cable was reeved over the derrick and attached to the nose of the bridge and used to lower it into a horizontal position. The cable was then detached and the hinged support on the front of the Dragon was disengaged. The Dragon could then drive clear enabling the following tanks to cross the bridge.

The Scissor Assault Bridge was mounted on a prototype Light Tank Mk V. Suggested by Captain SG Galpin RE, its practical application was achieved by Captain SA Stewart RE with design work by Mr DM Delany, a Scientific Civil Servant at EBE.

The bridge was 30' long and designed to span a 26' gap. It was made in two sections joined at the centre by a hinge in the bottom chord (lower section of the bridge when laid out). The folded bridge with the upper chord of one section on top of the tank was attached to the tank using a special framework with rollers. In its first stage of launching the folded bridge was moved to a vertical position at which point the rollers were resting on the ground.

Prototype No.3 bridge - draw bridge type carried 
              on a Churchill AVRE
Prototype No.3 bridge - draw bridge type carried on a Churchill AVRE
(Photo: IWM 4296)
A system of cables was then used to 'open the scissors' as the bridge tilted forward from the vertical about the rollers. The bridge was completely unfolded by the time it was horizontal across the gap and its carrier was then detached automatically.

The Wild Assault Bridge was designed and produced entirely by MB Wild & Co Ltd of Birmingham. It was also designed for a clear span of 26' and launched from a Light Tank VIB. The bridge was contained in a skeleton framework attached to the top of the tank. At this stage the bridge was in its two halves, the front or leading section being stowed below the second or tail section. Using a system of steel wire ropes and a travelling jib, the front section was projected forward to the front edge of the support framework. The second section was then lowered down automatically locked onto the leading section. The launch then continued and the travelling jib lowered the complete bridge into place. Whilst a good idea, it never worked successfully and was abandoned in favour of the scissors bridge. Nevertheless the idea was not forgotten and was successfully utilised by the German army in the 1970s in their Biber Tank Bridge mounted on a Leopard tank.

 

Second World War period

The start of Second World War (1939-45) with German 'blitzkrieg' into northern France gave major impetus to the development of armoured vehicles and associated equipment. The EBE immediately began work on a new Scissors Bridge, No 1 under the leadership of Delany. Its capacity was to be a Class 24 tracked load (24 tons) over a clear span of 30'. It was initially carried on the Covenanter tank but never saw combat in this form. It was subsequently upgraded with no change in design to a Class 30 tracked load and mounted on a turretless Valentine tank. They saw operational service in Italy, NW Europe and Burma.

The Tank Bridge No 2 provided a Class 60 tracked load and a Class 40 wheeled load over a 30' gap. Mounted on a Churchill tank its launch method was radically different. The bridge was in one piece and mounted on the tank which had no turret. The launching arm was attached by a pivoting arm mechanism with rollers to the front of the tank, the other end of the arm being attached to the centre of the bridge. The bridge remained horizontal as it was raised and then lowered by the pivot arm across the gap. Launch to lay time was 1.5 minutes.

No 2 Tank Bridge - Horizontal launch
No 2 Tank Bridge - Prototype 30ft - horizontal launch.
(Photo: IWM 3984)
Small Box Girder Tank Bridge Mark II
Small Box Girder Tank Bridge Mark II

The Tank Bridge, Small Box Girder was developed by 79th Armoured Division. The Division was to play a pivotal role on D Day with a whole range of specialist armoured assault vehicles known colloquially as 'Hobart's funnies'. The bridge was launched in one piece and was effectively a vehicle mounted drawbridge. It was attached to the front of an AVRE, where an A frame was also placed. The launch cable was attached to the front of the bridge and passed over the A frame to the winch cable housed on the back of the AVRE. It could be used across a 30' gap and more importantly to surmount a seawall up to 12' high. The bridge could be transported behind the AVRE using a twin tyred bogie.

 

The AVRE was based on the Churchill tank and retained its turret from which the 6 pounder gun was removed, its replacement being a 290mm Petard spigot mortar. This was designed by Major Millis Jefferis RE, whose fertile brain devised a whole armoury of explosive devices including the projector infantry anti-tank (PIAT). The spigot mortar launched a substantial demolition charge known as the 'Flying Dustbin'. With the turret turned 90 degrees a fascine could be carried as well.

Major General PCS Hobart served in First World War (1914-18) as a Sapper officer and transferred to the Tank Corps in 1923. An irascible individual who as a consequence was not very popular with his fellow officers, he was nevertheless a brilliant trainer and forward thinker. At the beginning of the war (1939) he was in Palestine where he raised the 7th Armoured Division (the Desert Rats) to a highly trained force. Subsequently sent back to the UK and forcibly retired he languished in the Home Guard as a Lance Corporal. From here he was rescued by Winston Churchill, who appointed him to command the newly formed 11th Armoured Division. When this division was sent to the Middle East Hobart was at the age of 58 appointed to command the 79th. The 'funnies' included the Sherman DD swimming tanks, the Crocodile flame thrower, Crabs, the Sherman flail tanks for mine clearance, and last but not least the Churchill AVREs. The 79th was a curious Division in that its component units were loaned out to other Divisions to support them in their offensive activities, they never fought as a composite Division.

f
Major General Sir Percy Hobart, Commander 79th Armoured Division and initiator of the 'Hobart's Funnies'
Apart from the various Assault Regiments RE, other units within the Division included the 22nd Dragoons and the 13/18th Royal Hussars. The units of the Division were always very much in the vanguard of D Day and subsequent fighting in NW Europe.
Churchill ARK - 1950's
Churchill ARK (armoured ramp carrier) - 1950's
(Photo: M Dagg - AE Branch REA)

The other significant bridging tank was the ARK (armoured ramp carrier). Based on a Churchill tank it had its turret removed and replaced by a trackway on top of the hull. This had hinged ramps at the front and rear. The ARK could be driven into the gap that needed to be bridged coping with up to 5' of water. The hinged ramps would then be laid onto the banks. If necessary they could be set out in tandem or even one on top of another, sometimes in conjunction with other tank launched bridges. The Burmark was a smaller version based on the Valentine chassis and used in Burma.

A new Inglis Assault or Mobile Bridge consisting of 13 bays of Mk III Inglis bridge enabling it to cross a gap of 80' was produced. The bridge was mounted on two tracked bogies and pushed into place by a tank. The Bailey Mobile Bridge which evolved from the foregoing was 170' long, again mounted on a caterpillar bogie and pushed into place by a tank. The Plymouth Bridge was another variation using Bailey components and mounted on a Sherman tank. The bridge was placed by the tank on which it was mounted with assistance from another tank to launch it. On the one occasion it was used operationally crossing the River Rapido in Italy the leading tank toppled into the river and was submerged. Two further variations of this were the Brown Bridge and the Dalton Bridge.

 

The Skid Bailey consisted of an assembled bridge with skids bolted onto the bottom of the panels. It was built to the required length away from the launch site and then pushed into position using a Churchill AVRE.

Post-Second World War period developments

Whilst armoured engineer units were reduced in number development of assault bridging continued to cope with the increased weight of new tanks that were being introduced.

The Number 3 tank bridge, a draw bridge type, succeeded the SBG Tank Bridge. With a Class 60 capacity it could bridge a 30' gap. It could accommodate vehicles as large as a Centurion tank and as small as a Jeep. It was launched by a Churchill bridge layer and was used operationally in the Korean War. A MkII version of the No 3 was developed to fill the gap left by the cancellation of the No 5 Tank Bridge, an up and over type, got to the trials stage only.

Tank Bridge No 6 was also an up and over type. This had a clear span of 45', it could be launched and placed from its Centurion carrier in 1.5 minutes. The practical difficulties of manoeuvring this 52' and 14' tracked behemoth through towns and villages in Germany must have been enormous. The bridge came into service in 1963 with 26 Armoured Engineer Squadron. It was designated the Centurion Bridgelayer (FV4002).

 

The successor to the No 1, Scissors Assault Bridge was the No 4 Tank Bridge. It was fabricated of aluminium alloy and could bridge a 30' gap. Only one prototype of this scissors type bridge was built before the project stopped.

The No 7 Tank Bridge was an up and over launched bridge, successor to the No 2 Tank Bridge. Designed to be launched from the Chieftan AVRE it got as far as a troop trial version before development was halted in 1965.

 

Development of the ARK continued well into the post war period. A pilot version of the Mark III ARK was built but work was abandoned. An FV203 and a Gas ARK were both begun but the projects were cancelled. The Churchill Linked ARK came into service in 1955. This could span a 65' gap. It consisted of a centre section fixed to the top of its carrier. The front and rear ramps each consisted of two folded sections which unfolded as they extended. They were described as linked, as two units were launched side by side and locked together to form a twin bridge. The Centurion ARK succeeded the Churchill in 1965. The end sections were launched in scissors fashion and it could span 75'. The Centurion ARK Mobile Pier [CAMP] was an ARK with no end ramps. This could be driven into a river and deployed centre stream parallel with the banks. It was then used as pier to support two No 6 bridges.

Cen
Centurion ARK (armoured ramp carrier), a Centurion AVRE on top (dozer blade on the front) - 1970's
(Photo: J Bacon - AE Branch REA)

The Churchill AVRE was developed as far as the Mark VII as a stop gap pending the introduction of the Centurion Mk V AVRE. The former was fitted with a new low velocity gun that could fire a 61lb HESH [High Explosive Squash Head] round. It was fitted with a fascine carrier and could have a dozer blade attached if needed. The Centurion AVRE (FV4003) succeeded it in 1963. It retained the 6.5" low velocity gun and fascine carrier. A fascine or roll of Class 60 trackway could be carried and it was fitted with a dozer blade. The dozer blade could be removed and a mine plough fitted in its place. It could tow a Giant Viper mine clearance system or a second fascine on a special trailer.

 
Centurion Bridge Layer (up and over)<br>
              as seen at the RE Museum
Centurion Bridge Layer (up and over)
as seen at the RE Museum

The next two bridges developed were designed to be launched from the Chieftan Bridge Layer (FV4205) known in service as the AVLB. The No 8 Armoured Vehicle Launched Bridge (No 8 AVLB) deployment began in 1974. This had an effective span of 75' and its full length was 80' - 40' when it was folded. The No 9 AVLB was an up and over bridge 44' long and could span a 40' gap. It came into service in 1978. Crossing gaps of greater than 75' could be achieved by Combination Bridging.

Typically a No 8 AVLB could be launched into a gap. A Bridge Layer would then drive onto this to launch say a No 9 AVLB from it onto the far bank. Careful reconnaissance was needed to ensure the river bed could support the submerged end of the first bridge. Stability is also an issue and the second and possibly subsequent bridges must be laid with great care.

Preliminary work on the Chieftan AVRE began in 1970 but was cancelled in favour of the Combat Engineer Tractor (CET). The requirement for the CET had been issued in 1962 and the first two prototypes were manufactured by Royal Ordnance in 1968. After a major redesign further prototypes which were now amphibious were delivered in the early 70s. Weighing 17 tons the CET has a rocket propelled earth anchor. This can be launched from the vehicle and once the anchor is bedded in it can use its own winch to draw it over an obstacle such as a river bank. It has a 1.7 cu.metre bucket which can be used to dig gun pits, remove obstacles etc. It can also tow the Giant Viper mine clearance trailer. This Rolls Royce powered vehicle with a crew of 2 came into service in 1978 and has proved invaluable in recent operations. One of the second batch of prototypes can be seen as the Museum. The Terrier, its successor, which is faster and more mobile with improved armour should succeed the CET in 2008.

Combat Engineer Tractor (CET)
Prototype of the Combat Engineer Tractor
as seen at the RE Museum

By 1983 the Centurion AVRE fleet were beginning to show their age and a successor was needed quickly. The introduction of the Challenger enabled Chieftan tanks to be released for conversion. A locally modified Chieftan AVRE was produced by 32 Armoured Engineer Regiment. Authority was given to produce 17 of these at the 21 Engineer Base Workshop at Willich in Germany. This very successful project was completed under the supervision of Lt Col JF Johnson RE, in 1987. Vickers Defence Systems undertook a further 48 conversions.

The next series of bridges were designed around the Challenger tank chassis. Assault Bridging was now referred to as Close Support Bridging (CSB). The Titan AVLB as the modified Challenger is known has 3 different bridges which it can be used to launch.
Close Support Bridge No Bridge type Length Span Carrier
No 10 CSB Scissors bridge 85' (26 metres) 21 to 24.5 metres  
No 11 CSB Up and over bridge 16 metres 14.5 metres Titan
No 12 CSB Up and over bridge 13.5 metres 12 metres Titan
They can be launched one after the other which is of particular value where a Combination Bridge is needed.

 

The Challenger based AVRE is known as the Trojan. Its attachments include a knuckle-arm excavator shovel and a full-width mine-clearance plough blade. It can of course carry the ubiquitous fascine and tow the Python rocket-propelled mine-clearance system. The Titan and Trojan are now in service.

 

Author: MW Stoneham, FoREM

Sources:
One More River to Cross Joiner J (Pen and Sword Books, Barnsley)
Churchill's Secret Weapons Delaforce P (Pen & Sword Books, Barnsley)
The British Army - a pocket guide 2006-2007 Heyman C (Pen & Sword Books, Barnsley)
Follow the Sapper. Napier G (Institution of Royal Engineers, Chatham, 2005)

Related links

Corps History Part 15 - The Corps between the Wars - tank development between the wars
Corps History Part 16 - The Corps and the Second World War - Assault Engineers (Hobart's Funnies)
Campaigns - Operation Overlord and the Royal Engineers - Assault Engineers (Hobart's Funnies)
Article - Military Bridging
Biography of Major General Sir Percy Hobart
   

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