The haunting history of the air-raid siren

The eerie soundtrack of modern conflict can trace its history back to the Great War.

Published 17 Mar 2022, 14:53 GMT
A child and mother run for shelter from air raids during the Spanish Civil War, Bilbao, ...

A child and mother run for shelter from air raids during the Spanish Civil War, Bilbao, Spain c.1937.

Photograph by World History Archive, Alamy

THE SPINE-TINGLING WAIL of air-raid sirens has become one of the defining sounds of warfare, a waxing and waning alert to imminent aerial threat. Since modern conflict and its technologies superseded the more confined practice of two armies squaring up across a battlefield, civilian populations have become victims of bombardment, everyday life menaced by the risk of an indiscriminate shell, mortar or bomb.

Faced with his danger, the same rise-and-fall sirens that sent people scurrying for shelter during the Second World War are now echoing along the streets of Ukraine’s cities as the terrible conflict unfolds. (Related: see and hear harrowing stories of Ukraine's refugees.

As early as 1907, H.G. Wells’s novel 'War in the Air' predicted the mounting threat of attack from the sky, four years before the first recorded air raid took place when Lieutenant Giulio Gavotti, fighting for Italy against the Turkish Ottoman empire in Libya, dropped grapefruit-sized bombs by hand from the open canopy of his aeroplane.

“Today I have decided to try to throw bombs from the aeroplane,” he wrote to his father. “It is the first time that we will try this and if I succeed, I will be really pleased to be the first person to do it.”

But it was Germany’s zeppelin attacks on Liege, Antwerp and Paris during the early months of the First World War, followed by raids on the south and east of England, that confirmed aerial bombardment as a deadly strategy of 20th-century combat.

The first bomb to fall on British soil landed on Christmas Eve, 1914 in the vegetable garden of Tommy Terson in Dover, followed days later by attacks on Great Yarmouth and King’s Lynn in January 1915. Modern warfare had become total warfare, and civilian populations were in the crosshairs.

(Related: How the Battle of Britain changed warfare forever.)

During the 1914-1918 conflict, 1,239 civilians, half of whom were women and children, were killed by bombs dropped by zeppelins. London alone was raided more than 50 times, attacks that arguably had a far greater psychological impact than the injury, death and destruction they rained down on the capital.

German airships terrorised Britain during the middle years of the First World War, and the movement of war away from the battlefields and into the civilian realm became a key recruitment driver for the War Office. Airships, due to their silent approach under cover of darkness necessitating searchlights to find and target, were nicknamed 'baby killers.' 

Photograph by United States Library of Congress

Bomb damage in Britain after the first aerial attacks by German aircraft. The main campaign against Britain started in January 1915 using airships launched by the German Navy and Army Luftstreitkräfte. The so-called Zeppelin raids used hydrogen-filled airships made by Zeppelin and Schutte-Lanz capable of travelling at close to 90mph, and carrying two tons of bombs.

Photograph by Colin Waters / Alamy

A propaganda postcard from Germany in 1915 pictures an airship bombing a British city. Approaching over the North Sea, cities hit included Hull, Great Yarmouth, Harwich, Southend and London. Later long-range raids targeted Liverpool and north-eastern cities such as Newcastle. Navigation was almost impossible, and targets – such as munitions factories and shipping infrastructure – were routinely missed, sometimes by hundreds of miles, leading to civilian casualties. German propaganda routinely hailed the raids successful. 

Photograph by Colin Waters / Alamy

When Gotha aircraft took over from the faltering zeppelin campaign in June 1917, the bombers’ first attack saw 14 aircraft drop 118 bombs on London, killing 162 people and injuring 426. This deadly assault forced the Government to act, constructing purpose-built air-raid shelters and developing an air-raid warning system.

There were already coastal look-out stations to spot enemy aircraft approaching across the Channel and pass on warnings, “to the proper military and police authorities and to certain factories and institutions where special precautionary measures are required in the public interest,” Sir George Cave, Home Secretary, told the House of Commons in 1917.

‘All minds at the same time’

But there was no standardised format for these warnings, relayed by telephone to vital war infrastructure, prompting Noel Billing MP to suggest “that whatever you do by way of giving warning be sure that the warning will convey the same thing to all minds at the same time, and not be construed by one man as his lunch whistle blowing five minutes before it is time, and by another man as an underground train or something blowing off a whistle.”

Billing proposed a system of six-horse power sirens suspended below hydrogen balloons that would float 1,500 feet above the ground.

“If the War Office, or the person in command of the air defences, gave warning to the Home Office that the raiding airmen were 15 miles off, the Home Office would know quite well that it would be 10 minutes before they could possibly be dropping their bombs here. Under those circumstances all a man would have to do would be to press a button, and within a minute 20 or 30 syrens [sic], which would be distributed all over London and the suburbs, would send out one long or two long or three short blasts, as the case may be.

“If a small red streamer were attached to the balloon it could be released electrically when the syren was sounded a second time, and that would indicate that the airmen were actually concentrating on the City, and that it was necessary to take shelter,” he said.

Left: A siren utilising compressed air on the rooftops of Paris during World War One, when the city was subjected to Zeppelin raids. Right: a hand-crank air raid siren is used by a member of the Croatian Defence Council (HVO)'s Rama Brigade in the village of Here during the conflict in Bosnia, 1994.

Photograph by GRANGER / Alamy (left) Johnny Saunderson / Alamy (right)

The cost of such a system, argued Billing, would be minimal compared to the “distress and excitement that it would relieve.” Furthermore, the same approach could be rolled out across the country; if the armed forces couldn’t protect people, it could at least warn them.

Sir William Pearce MP, however, was anxious about the “effect of constant warnings upon our working-class population… If I were managing Germany and I knew London was going to sound syrens and explode balloons every time hostile aircraft left the shores of Belgium I should send aeroplanes three times a week, and in a fortnight I should have London in such an extreme state of excitement that it would have disastrous effects.”

Pearce was supported by Sir Winston Churchill, unaware of the role that air-raid sirens would play in UK towns and cities less than a quarter of a century later. “In some of these towns where people have been repeatedly awakened up and disturbed needlessly by night alarms it has been found unsatisfactory,” said the cigar-smoking wartime leader in 1917.

The human factor

Alongside the wish to avoid spreading panic, there were also practical objections to sounding general alarms, explained Cave.

St Paul's Cathedral rises out of the smoke of a bombing by the German Luftwaffe, 1940. The period – which lasted between September 1940 and May 1941, was known as the Blitz, from the German blitzkreig (lightning war). 

Photograph by World Image Archive / Alamy

“To give a general warning in every case is a very serious responsibility, because it means the general stoppage of work, often for some hours, in some cases for the whole day,” said the Home Secretary. “Where a great factory is warned of a possible air raid it is quite natural that some of the men should desire to go home to see if their own families are safe, and they do not return to work on that day. That is human nature, and you cannot alter that. It is not only a question of loss of time and inconvenience, but it is also a serious loss in munition factories.”

This general distrust of how the working classes might react to the sound of a siren was a common theme of the time, writes Lynda Mugglestone, Professor of the History of English at the University of Oxford. If an attack was heralded, so was the prospect of seeing the invader, she says, highlighting the original definition of siren as a lure as much as a deterrent.

Siren warnings… might merely alert the populace to zeppelin presence in ways which tempt rather than deter,” says Mugglestone, citing an article published in the Evening News of 1916, which reported that, “the most surprising thing is the way everybody rushes into the street. Nobody takes any notice of the police warning; they just look upon these raids as a good show, and all are eager to miss nothing.”

Londoners would famously make use of the capital's underground stations as shelters during World War Two.

Photograph by Shawshots, Alamy

The first siren was invented by John Robison towards the end of the 18th century as a device to create a piercing sound. The noise is generated by a jet of air being forced through a high-speed rotating disc with evenly spaced holes around its edge. Cagniard de la Tour refined Robison’s invention, and it was fine-tuned again towards the end of the 1860s by Professor Joseph Henry, to create a steam-powered siren for use as a fog horn for lighthouses. 

Volume problems

The same need to broadcast a warning far and wide became a preoccupation of Britain’s Committee of Imperial Defence, which formed an Air Raid Precautions Sub-committee in 1924, concerned by the prospect of future attacks by bomber aircraft. 

As storm clouds gathered over Europe in the 1930s, the Home Office honed in on how far the sound of sirens could carry as it “turned its attention to instruments suitable for giving public air-raid warnings,” said Geoffrey Lloyd MP. An informal committee that included the engineer-in-chief of Trinity House (the lighthouse authority), as well as representatives from the National Physical Laboratory and Royal Engineers and Signals Board, conducted comprehensive trials from March 1937 to April 1938, placing ‘sound instruments’ on an elevated platform and deploying observers to record the strength of the signals on a four-point scale that ranged from ‘arresting’ to ‘just perceptible’, as well as using a noise meter from the National Physical Laboratory for an objective measure.

“It was found to be surprisingly difficult to transmit a clearly audible sound over any long range in a built-up area.”

The committee’s goal was to find a siren capable of a range of at least one mile. “To a very great extent the results of the trials were disappointing. It was found to be surprisingly difficult to transmit a clearly audible sound over any long range in a built-up area,” said Lloyd.

Only one siren passed muster; a four-horse power horizontal siren made by Gent & Co of Leicester, which in August 1938 was recommended by the Home Office to local authorities. They, in turn, had to determine how many sirens they required and where they would position them. Even a modest sized town such as Hastings in East Sussex, which had a population of about 65,000 people in 1939, required 19 fixed sirens, supplemented by nine auxiliary sirens, steam whistles and rattles (in case of a gas attack).

This rapidly developing network of pre-war sirens was accompanied by a Public Information Leaflet, published by the Lord Privy Seal’s Office in July 1939.

“When air raids are threatened, warning will be given in towns by sirens or hooters, which will be sounded, in some places by short blasts, and in other places by a warbling note, changing every few seconds. In war, sirens and hooters will not be used for any other purpose than this,” it said.

A Daily Express article from 4 September 1939 iterated the steps the public should take if they hear an air raid siren. The spelling is an archaic British version of the word. 

Photograph by Maurice Savage / Alamy
Left: Top:

A magazine from World War Two illustrates a comely village scene laid to waste by bombers – and contains information about what to do. During the 1939-1945 conflict many areas had air raid shelters within running distance, or so-called Anderson Shelters (named for MP Sir John Anderson, who was in charge of air raid precautions) which were issued to homeowners to erect semi-buried in their gardens.   

Right: Bottom:

An Royal Observer Corps soldier keeps watch for air attacks during World War Two, London, 1942. The sound of air raid sirens came to define the time.

photographs by GL Archive / Alamy

“The warning may also be given by the Police or Air Raid Wardens blowing short blasts on whistles. When you hear the warning, take cover at once.”

The leaflet went on to advise people to stay under cover until they heard the sirens or hooters sounding continuously for two minutes on the same note, “which is the signal ‘Raiders Passed’.”

In the case of a poison gas attack, “you will be warned by means of hand rattles. Keep off the streets until the poison gas has been cleared away. Hand bells will be rung when there is no longer any danger. If you hear the rattle when you are out, put on your gas mask at once and get indoors as soon as you can.”

The first air-raid sirens sounded in London within minutes of Neville Chamberlain's announcement of hostilities on 3 September 1939. It turned out to be a false alarm triggered by an unidentified allied aircraft, but it was not long before the rolling drone of sirens became a constant soundtrack to the home front as the Luftwaffe’s Blitz bombing raids intensified. From September 7, 1940 to 10 May 10, 1941, London was bombed on a nightly basis. 

The Cold War brought with it a new and more desperate threat – that of nuclear weapons. The infamous 'four minute warning' safety alert and the ‘protect and survive’ public information film of the 1970s (below) used sirens to warn of an impending nuclear attack from Soviet missiles. Bunkers were built across Britain, including this – the Civil Defence Nuclear Bunker near Cheltenham.   

Photograph by Jeff Morgan 08 / Alamy

As the Cold War heated up in the 1950s, air-raid sirens were redeployed as civil defence sirens to signal the four-minute warning of a nuclear attack. Across the Atlantic, a 138-decibel, 180-horse power air raid siren developed by Chrysler and Bell Telephone Laboratories was introduced to US cities in 1952 and still holds the record for being the loudest siren – capable of being heard up to 25 miles away.

Once a familiar sound whilst being tested everywhere from villages to the largest cities, the UK’s air-raid siren network was eventually decommissioned in 1993 at the end of the Cold War. It has taken almost three decades to develop its replacement. ‘Emergency Alerts’ is due for launch early this year and will deliver “an urgent and distinctive siren-like sound” to all mobile phones in the vicinity of a phone mast if there’s a danger to life nearby. The alarm will work on any phone, with no requirement for users to register their number, and be accompanied by on-screen advice about how to stay safe.

A modern twist on the fact the waxing and waning wail of a siren has truly embedded itself in the human psyche as warning of impending danger.

Jonathan Manning is a freelance journalist based in the East Midlands. Read more of his work for National Geographic here. 

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