3D Printed in Grey or Black
It was in the World War II era that the importance of armoured bridge layers, as well as combat engineering vehicles and armoured recovery vehicles, became fully clear. With the advent of Blitzkrieg warfare, whole divisions had to advance along with tanks, which were suddenly far out-pacing the speed of infantry soldiers. Besides leading to the advent of self-propelled artillery/assault guns, mobile anti-aircraft and armoured personnel carriers/cars, it became clear that functions like vehicle repair, mine-clearing, and the like would have to be carried out by armoured vehicles advancing along with tanks. Moreover, these forces would have to be able to cross all forms of terrain without losing speed, and without having to concentrate their thrusts over certain bridges (and the rising weight of armoured vehicles meant that fewer and fewer bridges could support these massed crossings). The only feasible solution to the dilemma posed by the mobility of all-mechanised armed forces was a dedicated platform that could improvise river and obstacle crossings at short notice and in otherwise inconvenient locations. Tracked and armoured, it was capable of operating right alongside combat units, crossing rough terrain and advancing in the face of light fire. To maximize on common parts and ease maintenance complications, they were usually based on existing tank chassis.
One of the earliest series-produced examples is the Brückenleger IV, a German AVLB based on the Panzer IV, which entered service with the Wehrmacht in 1940. Twenty were built, but problems of excessive weight limited the vehicle's effectiveness, and eventually all 20 were converted back to tanks. A new scissors bridge design was brought out by the British in response to the war, sufficient to support a 24-ton load over 30 ft (9.1 m). This was developed for the Covenanter tank. Eventually, it developed into a 30-ton capacity and therefore was carried by a turretless Valentine tank. It was used in Italy, North West Europe and Burma.