The Petroleum Warfare Department (PWD) was a government department established in Britain in 1940 in response to the invasion crisis during World War II, when Germany apparently would invade the country. The department was initially tasked with developing the uses of petroleum as a weapon of war, and it oversaw the introduction of a wide range of flame warfare weapons. Later in the war, the department was instrumental in the creation of the Fog Investigation and Dispersal Operation (commonly known as FIDO) that cleared runways of fog allowing the landing of aircraft returning from bombing raids over Germany in poor visibility, and Operation Pluto, which installed prefabricated fuel pipelines between England and France soon after the Allied invasion of Normandy in June 1944.
Inception
At the beginning of World War II, in September 1939, little fighting occurred in the West until the German invasion of France and the Low Countries in May 1940. Following the fall of France and the withdrawal of the British Expeditionary Force (BEF) from the beaches at Dunkirk in June 1940, Britain was threatened with invasion by German armed forces in 1940 and 1941.
In response to this threat of invasion, the British sought to expand the Royal Navy, Royal Air Force, and Army, replace the equipment that had been left behind at Dunkirk, and supplement the regular armed services with volunteer organisations such as the part-time soldiers in the Home Guard. With many types of equipment in short supply, frantic efforts were made to develop new weapons – particularly those that did not require scarce materials.
Although oil imports from the Middle East had stopped and most oil for Britain came from the United States, no shortage of oil existed at the time; supplies originally intended for Europe were filling British storage facilities and full tankers were kept waiting in American ports. The amount of petrol allocated for civilian use was strictly rationed and pleasure motoring was strongly discouraged. This was not, at least initially, because of a shortage of petrol, but because it might lead to large congregations of well-fuelled vehicles at popular places.
In the event of an invasion, the British would be faced with the problem of destroying these stocks lest they should prove of use to the enemy (as they had in France). By mid-June, as a basic anti-invasion precaution, wayside petrol stations near the coast had been emptied, or at least had their pumps disabled, and garages everywhere were required to have a plan to prevent their stocks being of use to the invader.If The Invader Comes. Ministry of Information. 1940, rule IV.
On 29 May 1940, as the evacuation of the BEF was in progress, Maurice Hankey, then a cabinet minister without portfolio, joined the Ministerial Committee on Civil Defence (CDC) chaired by Sir John Anderson, the Secretary of State for the Home Office and Home Security. Among many ideas, Hankey "brought out of his stable a hobby horse, which he had ridden very hard in the 1914–18 war – namely the use of burning oil for defensive purposes." Hankey believed that oil should not just be denied to an invader, but used to impede him. Towards the end of June, Hankey brought his scheme up at a meeting of the Oil Control Board and produced for Commander-in-Chief Home Forces Edmund Ironside extracts of his paper on experiments with oil in the First World War. On 5 June, Churchill authorised Geoffrey Lloyd, the Secretary for Petroleum, to press ahead with experiments, with Hankey taking the matter under his general supervision.
Donald Banks Donald Banks had served with distinction in World War I, winning the Distinguished Service Order and Military Cross. He joined the civil service, and in 1934, he was made Director-General of the Post Office, he then moved to the Air Ministry and served there as Permanent Under Secretary from 1936 to 1938. Due to overwork, Banks was given lighter duties, including a mission to Australia to advise on aircraft production and a job at the Import Duties Advisory Committee. During this period, Banks was in the Territorial Army Reserve. When hostilities broke out in September 1939, the advisory committee was abolished and he was free to serve in the armed forces.
Banks was soon posted as air attaché to the quartermaster general of 50th (Northumbrian) Infantry Division – a first-line division of the Territorial Army. Banks got on well with his commander, Major-general Giffard LeQuesne Martel. Banks admired his leadership and his enthusiasm for experimentation and improvisation. In October 1939, the division was sent to the Cotswolds, and in January 1940, it was moved to France.
When Germany attacked in May, the division was heavily involved in the fighting around Arras and was later withdrawn to the coast. Banks later recalled looking out to sea from a clifftop and seeing "an awe-inspiring sight [...] A few miles away an oil tanker had been bombed or had struck a mine. Masses of the blackest smoke pillared up into a gigantic pall in the sky while in the vast lake of fire, spreading it seemed for miles on the water a flame blazed and leapt like an angry volcano [...] I was often to recall that scene in subsequent days of Flame Warfare". The division was evacuated to England.
Early in July 1940, Banks was summoned to the presence of Geoffrey Lloyd, who explained the vision that Hankey and he shared: "Flame all across Britain" he said, "ringing the coasts, spurting from the hedges and rolling down the hills. We will burn the invader back into the sea."
Considering Lloyd's ideas over the next few days and consulting with other soldiers, Banks found both professional scepticism and enthusiasm. Banks, a man who said he preferred the prospect of real fighting over "Whitehall warfare", was not himself keen and his first instinct was to suggest that petroleum weapons should be developed locally. Lloyd would have none of it and Banks was ordered to report to him for special duties. On 9 July, cutting through red tape, the Petroleum Warfare Department was created.
The Petroleum Warfare Department started on 9 July 1940 in three small rooms. They were independently administered and financed with a few staff entirely lacking in technical knowledge.
Flame traps
PWD took inspiration from events that happened during the retreat to Dunkirk in June 1940. One example occurred when Boulogne was attacked in the early hours of 23 May and the road to Calais was cut. In the defence of Boulogne, a group of pioneers under Lieutenant-colonel Donald Dean , had improvised a road block made of vehicles and piles of furniture from bombed-out houses. An approaching tank began to push its way over the obstruction, as Dean wrote:
The newly formed department quickly made arrangements for some practical experiments at Dumpton Gap in Kent. These were the source of some excitement for witnesses, who included the pilots of enemy planes. Many of the first ideas to be tried proved fruitless, but experience quickly led to the development of the first practical weapon - the static flame trap.
Static flame trap
A static flame trap allowed a length of road, typically , to be covered in flame and smoke at a moment's notice. The weapon was a simple arrangement of perforated pipes placed alongside a road. The pipes were steel, in diameter and drilled with holes at angles carefully calculated to cover the road evenly. The perforated pipes were connected to larger pipes that led to a tank of fuel in a raised position. The fuel mixture was 25% petrol and 75% gas-oil that was contrived to be of no use as motor vehicle fuel should it be captured. All that was required to trigger the weapon was to open a valve and for a Home Guard to throw in a Molotov cocktail creating an inferno. The ideal location for the trap was a place where vehicles could not easily escape, such as a steep-sided sunken road. Some trouble was taken with camouflage; pipes could be hidden in gutters or disguised as handrails; others were simply left as innocent-looking plumbing.
All the required pipes and valves could be obtained from the gas and water industries with little modification required beyond drilling a few holes. In general, gravity was all that was required to provide sufficient pressure for the fountains of oil but, where necessary, pumps were provided.
Later versions were a little more sophisticated; remote ignition could be achieved in a variety of ways. In one system, called the Birch Igniter, the pressure of the oil at the end of the pipe would squeeze glycerine from a rubber bulb; the glycerine would fall onto a container of potassium permanganate, which would then ignite spontaneously. Another method was to run a pair of small rubber tubes, down one of which would be passed acetylene and the other chlorine; when, at the far end, these two gases were allowed to mix, there would be a spontaneous ignition. This system had the advantage that it could be turned on and off repeatedly. The development of the flame fougasse (see below) provided a method of remote electrical ignition that could only be used once, but was virtually instantaneous.
Some 200 static flame traps were installed, mainly by the employees of oil companies whose services were placed at the disposal of the government.
Mobile flame traps
In addition to the static flame traps, mobile units were created. The main design used an otherwise redundant tank mounted on the back of a 30 cwt lorry, just behind the cabin. In the middle of the remaining space was a petrol-driven pump and either side of this was stored of armoured rubber hose. Two nozzles were provided with a primitive sight and with spikes for pushing into the ground. Gas tubes for chlorine and acetylene gas were provided for ignition. The resulting jets of flame had a range of .
Because a shortage of pumps existed – they were badly needed for fighting fires started by bombing – a simpler type of mobile flame trap was also designed. This consisted of a number of diameter pipes welded shut to make a long cylindrical drum, which was filled with of petrol-oil mixture and pressurised with an inert gas. Five of these cylinders could be transported on the back of a vehicle, and at a weight just under , could be deployed reasonably quickly wherever an ambush was required. The cylinders would be placed at intervals along a road, each with a short length of hose leading to a nozzle secured by ground spikes. Flow was initiated by a pull string that opened a valve and ignition was provided by Molotov cocktails.
Flame fougasse
The Petroleum Warfare Department soon received the assistance of Henry Newton and William Howard Livens, both known for designing mortars during the First World War.
During the First World War, Livens had developed a number of chemical-warfare and flame-throwing weapons. The largest of his works was the Livens large-gallery flame projector, which could project burning fuel . His best-known invention was the Livens projector: a simple mortar that could throw a projectile containing about of explosives, incendiary oil, or most commonly, poisonous phosgene gas. The great advantage of the Livens projector was that it was cheap; this allowed hundreds, and on occasions thousands, to be set up and then fired simultaneously, catching the enemy by surprise. Both Livens and Newton experimented with field-expedient versions of the Livens projector using commercially available five-gallon drums and tubes. Newton experimented with firing milk bottles filled with phosphorus using a rifle. None of these experiments were taken forward.