This article was first published in the September 2014 issue of BBC History Magazine


There was a mood of tension in the air that bright morning in the summer of 1940, as the military personnel, scientific experts and government officers gathered at the top of the cliff overlooking the Solent estuary in Hampshire. Next to this distinguished group stood a row of 10 large Scammell petrol tankers, from each of which stretched a long pipe, snaking down the 30‑foot-high cliff, across the shoreline and out into the sea. At a given signal, the valves on the 10 petrol tankers were opened, and almost immediately the pipes began to deliver oil into the water at a rate of 12 tonnes an hour.

What happened next profoundly impressed the gathering. A series of flares and sodium pellets were fired into the sea. As they ignited the oil, a gigantic wall of flame raged up from the surface with such intensity that it seemed as if the sea itself had begun to boil, while thick black smoke climbed thousands of feet above the fiery barrage.

The remarkable sight of the burning sea sent a wave of excitement through the military and the government. Why? Well this experiment, held at Titchfield on 24 August 1940, took place at a moment when the fate of Britain hung in the balance. With most of western Europe now under the control of Hitler’s Reich, an imminent German invasion seemed inevitable.

In the skies over southern England, the RAF fought heroically to stop the Luftwaffe gaining air superiority, one of the essential conditions for any seaborne assault launched by Hitler. But now the British authorities felt that they might have another weapon that could be highly effective against an invader. One of those who witnessed the Titchfield trial, Vice Admiral Sir Geoffrey Arbuthnot, called it “an outstanding success”, adding: “I do not believe that any landing forces would attempt to pierce the flames even if the force were aware of the width of fire.”

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British resolution

Yet, for all the combustible inspiration it provided, the burning sea trial was hardly unique in the summer of 1940. Britain’s determination to resist a German assault could be seen in everything from the creation of new types of bombs to the mass installation of road blocks. With the invasion looming, Britain bristled with a fortress mentality.

This was a land where signposts were removed from every road, where 18,000 pillboxes were built and where beaches were protected by miles of barbed wire.

The idea of Britain as a well-prepared nation, ready for a German attack, runs counter to the usual narrative of 1940. According to the myths about this period, Britain was in a state of ill-defended, poorly equipped weakness, thanks to years of complacency from prewar governments.

This chronic feebleness was supposedly symbolised by the laughable inadequacy of the Home Guard, subsequently immortalised in the TV comedy Dad’s Army, whose weaponry was said to be as woeful as the calibre of its recruits. According to this account, Britain was only saved from inevitable defeat and subjugation by the courage of the Fighter Command pilots.

There is another fashionable argument which holds that the Germans were never serious about invasion, which meant that Britain survived, not through her own efforts, but simply because of the enemy’s hesitations. There is no doubt that Hitler was ambivalent about a direct attack on southern England, partly because of his fears about marine operations. “On land I feel like a lion, but at sea I am a coward,” he once said. Other factors that fuelled his doubts were his admiration for the British empire and his belief that London would be forced by military realities to negotiate.

Nevertheless, after the fall of France in mid-June, the German High Command embarked on extensive preparations for an invasion, especially the creation of a vast, makeshift fleet of barges to carry the invasion force, which would ultimately comprise 260,000 troops, to the southern English coast. In a series of military conferences from early July 1940, the Germans worked out in great detail the invasion plan, to be called Operation Sealion, even down to the number of guard dogs that would take part in the landings.

But the belief that Britain was hopelessly ill-prepared to tackle the invasion threat is a romantic fallacy that downplays the dynamism of Churchill’s government and the public. The Finest Hour belonged not just to the RAF but to the wider nation. Contrary to the image of institutionalised chaos in 1940, British military and political officialdom was tough, resilient, well organised and resourceful. The political ruthlessness that brought Winston Churchill to power in early May 1940, when the Tory party rebelled against the ineffectual leadership of Neville Chamberlain, was reflected in a host of other initiatives, like incarceration of all enemy aliens and political extremists, the destruction of the French fleet at Oran to stop it falling into the hands of the enemy and the control of the entire German spy network in Britain after turning several agents.

A disguised British pillbox
The British built 18,000 pillboxes to repel a German assault. This one is disguised as a garage. (Photo by Fox Photos/Hulton Archive/Getty Images)

In the same ruthless spirit, General Edmund Ironside was sacked as the commander-in-chief of home forces in late July 1940, despite his popularity with the public, because Churchill regarded him as too pessimistic and defensive. One of his critics, the military historian Basil Liddell-Hart, even described Ironside as “gaga”. His replacement, the Ulsterman General Alan Brooke, was a figure of much greater natural authority.

The British were also far more efficient than is often recognised. A host of massive logistical exercises were carried out with barely a single hitch, like the shipment of all the Bank of England’s gold reserves to Canada, the evacuation of schoolchildren from London, and the transfer of national art treasures to remote hiding places.

Similarly, British military defences were stronger than historical mythology suggests. The Royal Navy, which would have had the primary responsibility of defending the Channel, had 10 times as many destroyers as Hitler’s Kriegsmarine, while the regular army had an overall force of some 1.3 million men in uniform at the end of July 1940.

That total excludes the Home Guard, which has long been subject to mockery. But actually the arming of this force, far from being an embarrassment, is a graphic illustration of how successfully Britain prepared to counter Sealion. It is true that in the early days of May 1940, just after the War Office had announced the formation of the Local Defence Volunteers, as the Home Guard was originally known, the weapons for the individual units could hardly have been more primitive. Muskets, blunderbusses, swords, truncheons, golf clubs, crossbows and even chair legs all found their way into the LDVs’ arsenal. One unit in Lancashire was equipped with Snyder rifles held in Manchester Zoo and last used during the Indian Mutiny of 1857.

Subject to mockery

But this picture had dramatically changed by August 1940, thanks to the import of weapons from America, the bulk of which were 615,000 M1917 rifles, dating from the First World War. These arms are often described as poor and antiquated, but they were just as good as the standard issue Lee Enfields used by the regular army. Indeed, in ballistic terms, they were superior to the Lee Enfields because their .30 calibre rounds had a flatter trajectory. One sniper instructor, Clifford Shore, described the M1917 as “probably the most accurate rifle I ever used” and a “splendid weapon”.

The same was true of other American weapons supplied to the Home Guard, blowing apart the Dad’s Army caricature of pitchforks and broom handles. A total of 25,000 Browning Automatic Rifles, with a rate of fire of 500 rounds per minute, and 22,000 Browning water-cooled machine guns found their way to Home Guard units before September 1940, by which time more than 900,000 volunteers were in uniform.

Less orthodox weapons than the M1917 and Lee Enfield rifles also played their role in Britain’s land defences. These included: the Self-Igniting Phosphorous (SIP) grenade made by the Midlands firm of Albright and Wilson, which was essentially a half-pint bottle filled with an inflammable mixture of white phosphorous, benzene, and crude rubber; the anti-tank Number 74 Grenade, colloquially known as the ‘Sticky Bomb’, made up of a spherical glass flask filled with nitroglycerine and attached to a wooden handle, giving the weapon a resemblance to a toffee apple; and the McNaughton mine, an underground pipe, filled with explosives, that could be placed under bridges, roads and railways to halt the advance of the enemy.

Far more deadly were the poisonous gas weapons that Britain planned to deploy against the German invader, in defiance of the Geneva protocols on the conduct of war. Some were appalled at the idea of such illegality. Major General Desmond Anderson of the army’s Imperial General Staff argued that such a move would be “a departure from our principles and traditions”, which would prompt “some of us to begin to wonder whether it really mattered which side won”.

But neither the chiefs of staff nor Churchill had any time for such sensitivities when Britain’s survival was at stake. “We should not hesitate to contaminate our beaches with gas if this would be to our advantage. We have the right to do what we like with our own territory,” said Churchill. Accordingly, the British armed forces were equipped to use gas, both on land and from the air.

Members of the British Army during World War II
An anti-aircraft-gum team pictured in May 1940. By July of that year, the British Army had 1.3 million men in uniform. (Photo by Fox Photos/Getty Images)

By the summer of 1940, the army had 10 companies that were trained to handle chemical weapons. Their substantial stores were made up of 25,000 shells filled with mustard gas, 15,000 ground bombs, and 1,000 chemical mines, as well as 10 ‘Bulk Contamination Vehicles’ and 950 projectors that could fire chemical-filled drums. Meanwhile, Bomber Command had 16 squadrons that were designated for duty in either spraying gas or dropping chemical bombs on the enemy. By the autumn of 1940, Britain’s stock of chemical weapons amounted to 13,000 tonnes.

The country also had huge reserves of petroleum, which explains why the government was willing to pursue such fuel-hungry experiments as the marine flame barrage.

Supplies of petrol were also used in the development of innovative land weapons against the invader, like the static flame trap, which consisted of an oil tank connected to a network of perforated steel pipes, laid by the road, which could let off huge jets of fire at the enemy once ignited. There was also the lethal ‘flame fougasse’, a barrel full of an oil mixture that, when detonated, could cover a large area with burning liquid. “Nothing could have lived in it,” said Fred Hilton, a Lancastrian soldier who witnessed one demonstration of this weapon.

Members of the Home Guard practise their hand grenade-throwing skills
Members of the much-maligned Home Guard practise their hand grenade-throwing skills using pieces of concrete and lead piping, c1940. (Photo by Hulton Archive/Getty Images)

In mid-September 1940, just when German preparations for Operation Sealion were meant to have been completed, British propaganda brilliantly exploited these experiments in petroleum warfare to heighten apprehension among the Reich’s planners and seaborne forces. This was done by using intelligence networks on the continent to spread rumours about charred corpses of German soldiers being washed up on the beaches of both sides of the Channel. Such rumours carried a degree of credibility because large numbers of German troops had indeed been burnt in heavy RAF bombing raids on the enemy barges in the Channel ports. British radio broadcasts and more than a million leaflets added to the fear by giving mock English language lessons for the putative invaders. “See how well the captain burns,” was one sarcastic phrase in this British material.

All this activity, from the propaganda to the RAF bombing raids, from the continuing resilience of Fighter Command to the growing strength of the beach defences, cast severe doubts in the minds of Hitler and his military chiefs about Sealion. Faced with all the evidence of such a determined foe, the gamble seemed too great. On 17 September 1940, Hitler announced an indefinite postponement of Sealion. Officially, the invasion plans remained in place until the spring of 1941, partly to keep Britain on the defensive, but after September, Hitler never had any intention of implementing them. Thwarted in the west, his thoughts turned to the east, with ultimately disastrous consequences.

Countdown to the invasion

14 May 1940 War secretary Anthony Eden announces the formation of the Home Guard to tackle potential German airborne landings.

21 May 1940 Admiral Erich Raeder, commander of the German navy, meets Hitler to discuss for the first time a possible invasion of England.

3 July 1940 The Royal Navy sinks a large part of the French fleet at Mers-el-Kebir in Algeria to prevent it falling into German hands. Hitler is furious at Britain’s defiance, but the USA is impressed.

16 July 1940 Hitler issues Führer Directive No 16, ordering detailed preparations for an invasion of southern England between Dorset and Kent, to be called Operation Sealion.

19 July 1940 Alan Brooke replaces Edmund Ironside as the commander of home forces. Brooke’s anti-invasion strategy places a new emphasis on counter-attacking mobility by the army.

13 August 1940 Adlertag or Eagle Day, the start of the great aerial offensive by the Luftwaffe, which was meant to give Germany air superiority over southern England.

7 September 1940 The beginning of the Blitz leads to widespread alarm in Britain that the invasion is under way. The Home Guard is called out and church bells rung across the country.

15 September 1940 German preparations are meant to have been completed, with 2,000 invasion barges now gathered in the Channel ports. But RAF bombing of the fleet undermines German confidence.

17 September 1940 Hitler reveals his intention to postpone Sealion indefinitely.


Leo McKinstry is a journalist and author who has written numerous history books, including several on the Second World War era.