Bogged vehicles and grounded aircraft are millstones around the neck of an army; if its transport ceases to flow, offensive action becomes impossible and defence a matter of uncertainty. How perplexing ground-problems have been ingeniously solved for our forces in France and elsewhere, by the provision of portable roads and airstrips, is explained by Lieut.-Col. R. M. LESTER.
As our armies advance towards Hitler's inner lines of defence; portable roads and aircraft runways are being laid in forward positions, thus enabling our tanks and other vehicles to move over the worst kind of ground, and our aircraft to land on and take off from advanced bases. Tremendous use was made in North Africa, Sicily and Italy of these "magic carpets", and on them we were operating Allied aircraft from the Normandy beach-head shortly after D-Day. Before the end of the first day of our landing in France our armoured vehicles and lorries were moving along these portable roads.
This was made possible by the development of what is known as Sommerfeld Track, the principle of which is that of a spider's web, as already roughly copied by man in the tennis racket. It is a light metal carpet made of wire netting strips, reinforced with steel bars. The engineers lay it in rolls of 25 yards, about 10½ feet wide, with loops at the edges. For aircraft runways widths are linked together by threading the steel bars through the marginal loops; then a bulldozer or caterpillar tractor stretches the whole thing taut, the runway then, being fastened to the ground by steel spikes driven at the outer edges. Although the landing strip has not the usual hard surface it is perfectly adequate for heavy aircraft.
The material is so light and portable that a runway can be carried in eighteen 12-ton lorries; the material for a concrete runway of the same dimensions would need 2,500 such lorries. Thus considerable economy in transport is effected. The first of these runways was tried out on an English downland during an Army exercise without any preparation other than levelling the site. Just before this war experiments had been carried out in Palestine, and these were continued, after the outbreak of war, in a small country garden in England. Early in 1940 the Army authorities carried out tests, and this material of light weight, in easy portable loads, was found to be admirably suited to the purpose. So production was started, at first in a small workshop, later on a rapidly expanding scale in the factories.
In 1941 the first operational track was laid at a fighter station, and it is still in use and giving every satisfaction. Attention was turned meanwhile to the production of special tools that would help to reduce the time taken in laying the track. It was early in 1942 that selected units of the Royal Air Force succeeded in laying a track in 11¾ hours. The next development was that of wooden flexboards, on the principle of continuous duckboarding; these are laid as wheel tracks, transversely arranged, and held closely together with steel bands which are secured through the timber, the ends of these bands being formed into loops and welded.
The boards are flexible, to suit uneven ground, and can bridge small gaps and holes. Heavy lorry loads can be transported over grass runways on airfield construction jobs by making use of these boards, and no wheel ruts are left in the grass. The R.A.F. uses them for extricating bogged bombers, and for aircraft standings. A great advantage is that they can be removed from site to site as required, for use over and over again.
On D-Day, as transports reached the Normandy beaches Royal Engineers were ready to perform their particular task without further orders. Sappers and pioneers leapt overboard with their pickets and slegdehammers and started unrolling the first twenty-five-yard strip of Sommerfeld Track. With our fighters and anti-aircraft batteries giving cover protection, lorries were slowly moving along the tracks as they were laid out. These were linked up with the nearest permanent roads, and soon tanks and other vehicles were proceeding in great convoys. Ducks - our amphibious carriers - ran straight out of the sea up these newly laid tracks, sometimes negotiating steep inclines. They were each carrying over two tons of bombs, for the use of our aircraft in their task of blocking the enemy's lines of communication.
Four Canadians, flying Spitfires, were the first pilots to land there. A captain of the Royal Engineers was in charge of a unit at work on the airfield, which they had set up in about 36 hours. They had been training, of course for this work for many months, becoming as proficient in track drill as an infantryman in platoon drill. Every hour found the airfield nearer completion, and when the pilots landed there again the following morning it was fully equipped for servicing aircraft and for carrying out minor repairs.
It is possible to overcome the problem of marshy ground by laying a matting under the track. As an example of how the greatest difficulties in this direction can be speedily overcome, there is the case of a piece of ground near the Volturno River, in Italy, which our Engineers found to be little more than a swamp. Yet in a matter of hours they had levelled the ground, laid out the rolls of steel matting, and converted it into a fully serviceable airfield.
President Roosevelt, in a message to Congress, stated that - among other material - 44,500,000 yards of Sommerfeld Track had been received by the United States from Britain under Reverse Lend-Lease. There is no doubt that this is one of the outstanding inventions which has made possible our invasion of Europe. What would we not have given to have had such facilities in the last war, when we recollect the endless bogging of vehicles in the appalling mud of the Somme! In Viscount Allenby's campaign, too, the problem of transporting vehicles over the desert sand was a very serious one, and sheep hurdles were put down to form as firm a surface as possible. The Germans in the last war requisitioned all the curtains they could get hold of in East Prussia, nailed them to wooden frames and placed them on the lake ground in the region of the Masurian lakes, thus providing very temporary roads for their vehicles.
The "battle of the building-up" in all theatres of war owes much to these portable roads. And there is a post-war aspect of this invention: it will prove invaluable in the making of temporary roads wherever new territories are exploited, or where building takes place on unpromising sites.
The Bayeux by-pass in Normandy, along which Allied transport is seen passing, was swiftly laid with the Sommerfeld Track which is described in the accompanying article. Without that ingeniously devised track, construction of the road would not have been possible in such a short time as was necessary for our advance. Photo, British Official.