The Codebreakers: The True Story of the Secret Intelligence Team That Changed the Course of the First World War (15 page)

The aftermath of a Zeppelin attack on Bartholomew Close, London, 1915

On 14 June, Hoy wrote that ‘decoded messages showed that L10 had left her shed at Nordholz at the same time as SL3, but there was no certainty as to her destination’. They were heading for Hull and other targets in the north-east. August was relatively quiet; then, over successive nights in early September, the capital got the worst of it: 40 dead, more than 100 injured, as both the East End and central London were blasted. A bus was flattened near Bloomsbury, while at Holborn a 660-tonne bomb created an eight-foot-deep hole in the ground.

The raids were getting bigger. According to Hoy, shortly after 5 p.m. on 13 October, Room 40 decoded a wireless message which showed a serious raid was pending. Half a dozen Zeppelins were involved and once again London was the primary target. Casualties were high: Hoy called it ‘a fearful night’ during which 71 people were killed and over 120 so badly hurt that ‘probably few of them will survive to tell the tale’.

By early 1916, the Zeppelins were travelling even further afield. Room 40 decoded wireless intercepts that served as a warning of a serious attack on Liverpool. Due to bad weather, they didn’t make it that far but still managed to offload 376 bombs, mostly incendiaries, on Manchester, Scunthorpe, Hull, and Walsall in Norfolk, where a stunned witness described the terrifying moment a tram full of passengers was hit: ‘the blast broke its windows. A piece of glass struck the Mayoress who was riding in the tram and she died from her injuries.’

Throughout this onslaught the army had continued to grapple with the navy for control of home defence until a compromise was eventually reached on 10 February 1916. The Admiralty was to focus on the Zeppelins while they were over the sea, the army while they were over the UK. Room 40’s intelligence remained vital, as it alerted the seaplanes of the RNAS, giving them the chance to hunt down the Zeppelins before they reached the mainland.

Hoy described how ‘we learned from the German wireless that another raid was to take place. This was decoded so quickly that by 3 p.m. we were able to inform the Eastern Naval Command that there were 12 airships over the North Sea.’ The RNAS sprang into action: ‘our seaplanes … were at once ordered out from Harwich … L13 reported by wireless at about 10 o’clock that she was hit.’

Meanwhile, at the War Office, Malcolm Hay already had four officers on wireless duties. In March, they left MI1(b) and formed MI1(e) to deal exclusively with the Zeppelin menace. Two of them collated the messages that were received by the special aerial on the roof of the building within 60 seconds of transmission, while the other two attacked the daily cipher key. The unit was connected by direct line to the WO telegraph section. It forwarded the data by pneumatic tube to Room 417, the main control centre. From there the information was called through to GHQ Home Forces. One squadron leader described the scene. A large map was laid out on a table. Sitting round it were ‘a number of operators … receiving information on telephone handsets as it came in’ and plotting it on the map, making it ‘possible for the GOC to see the position of the raid at a moment’s glance’.

With the DF stations and the codebreakers leading the way, the British had at their disposal a formidable intelligence-gathering system that produced a clear picture of the scale and timing of each raid. However, all this information was worthless unless the air force could actually destroy the enemy. Due to inadequate firepower, it couldn’t. The planes simply didn’t have ammunition powerful enough to penetrate the monster’s skin. They were further handicapped by lack of altitude. Unable to operate higher than 13,000 feet, they were no match for Zeppelins that were still comfortable at 18,000 feet. Speed was an issue as well. The airships could climb 1,000 feet a minute; British aircraft took ten times as long to cover the same distance.

As a consequence, the Zeppelins continued their grisly work without loss. On 5 March 1916, Hull’s waterfront and docks were attacked. The damage was considerable and the commander of the raid ‘saw whole structures toppling into ruins until that section took on the appearance of an immense black crater on the snowy landscape’. Like other targets in the north, Hull was practically defenceless: no guns or planes were available to meet the threat. Afterwards, an angry mob stoned an RFC vehicle and attacked one of its officers. A few weeks later, a terrible tragedy unfolded in Cleethorpes when a bomb landed on a Baptist chapel full of soldiers, leaving 32 dead and 48 injured; a member of the medical team that arrived on the scene likened it to Dante’s ‘Inferno’.

During July, poor weather prevented a series of raids; then, on the night of 2–3 September 1916, came the biggest one of the war so far, involving 16 airships that ranged across the country, targeting Nottinghamshire, Lincolnshire, Hertfordshire, Sussex and London. However, what might have been another deeply dispiriting few hours of indiscriminate, unopposed carnage proved to be the night the tables turned.

The technological breakthrough that made the difference was the work of a New Zealand engineer, and came in the form of an explosive soft-nosed bullet loaded with phosphorus that flattened on impact, creating a large hole. Used in combination with incendiary bullets and tracer bullets, known as ‘sparklets’, they finally gave the air force the means to cause significant damage.

During the Saturday night in question, 2/3 September, SL11 was shot down at Cuffley Hill in Hertfordshire. News that one of the beasts had been slain was greeted by a wave of euphoria, a great release of accumulated stress and tension. The next day became ‘Zeppelin Sunday’. Special trains were laid on from King’s Cross to ferry curious and jubilant crowds to the crash site. The landlord of the local pub charged twopence entry.

One of the first visitors to inspect the wreckage was Blinker Hall. In May, the Germans had changed their code books. The HVB, used by the Zeppelins, was replaced by the
Allgemeines Funkpruchbuch
(AFB). For the first time, Room 40 was operating in the dark. Hall was desperate to get his hands on a copy of the new codes, especially as they were being adopted by the enemy’s submarines as well. Until he did – and there was no guarantee that he would – Room 40 had no alternative but to begin the painstaking and laborious business of trying to reconstruct the AFB codes from scratch by trawling through the plethora of available messages for clues.

The obvious choice for this task was Dilly Knox, now firmly established as Room 40’s leading codebreaker. By early 1916, Dilly had his own office, Room 53, a tiny space dominated by a huge desk and a bath that he had had specially installed. Lying in a steaming tub for hours helped stimulate Dilly’s thought process as he pondered codebreaking conundrums. Though his work was often presented ‘in inky scribbles on sheets of dirty paper’, sometimes sopping wet from bathwater, there were no doubts about his ability.

With nothing to go on except messages sent in the new code, which consisted of three-letter groups, Dilly, searching for an identifiable pattern, noticed that the word ending ‘en’ was repeated throughout in a similar position. He realised that this construction resembled a poetic metre known as dactyls. This suggested to him that the wireless operator responsible had encoded his signature, which identified him as the sender, by using part of a poem.

Dilly was no expert on German literature, so he took the messages to someone who was: Professor Leonard Willoughby. Willoughby examined them and decided they came from a poem by Schiller. He gave Dilly the full translation of the relevant lines, and armed with these Dilly was able to identify ten new code words, which he used as the basis for further reconstruction of the AFB. Nevertheless, it might take months for him to crack the whole thing open.

The best hope of resolving the crisis, therefore, was for Hall to recover a copy of the code book from a downed Zeppelin. When SL11 met its doom on 3 September, he was ready to act fast. According to Hoy, ‘Hall rushed to the scene as soon as the news of the fall of the blazing Zeppelin reached him, but by the time he reached Cuffley, the wreckage had burned itself out.’

Then, three weeks later, during another massive assault, L33 was hit several times after terrorising the East End and landed in a field near Chelmsford. Miraculously, both ship and crew survived intact. Having destroyed their code books, the men wandered to a village and were taken in by local police. That same night, 23–24 September, L32 was shot down at Snail’s Hill Farm near Billericay in Essex. A fellow Zeppelin commander described the moment it was hit: ‘suddenly a red light shone out vividly through the darkness … a vast ball of fire hung in the heavens … and then like a gigantic torch, the ship dropped faster and faster to earth. She crashed to the ground and continued to burn … our grief was overwhelmed by horror.’

Trooper Charles Williams was one of those assigned to guard the wreck, which ‘burnt well into the early hours of the morning’. The roads leading to it were jammed with cars and people keen to get a look. By dawn, thousands had gathered. Williams and his fellow soldiers made a tidy profit selling bits and pieces of the wreckage, while local blacksmiths converted scraps of metal into bespoke souvenirs.

Hall was also on the hunt for mementoes from the remains of L32. He had a team on site before the other scavengers arrived and they were rewarded for their efforts. The new code book, somewhat charred, was retrieved from the smouldering remains.

From that point on, the law of diminishing returns applied. In the next six months, four more Zeppelins went down in flames. A further seven crashed in the sea. Not a single crew member survived. Another Zeppelin was blown up by RNAS planes during a bombing raid on its sheds at Trondern: this attack was the first ever air strike launched from a ship, HMS
Furious
. The aircraft carrier was born.

Though new Zeppelins were being built, the loss of so many highly experienced personnel was much harder to bear. The final blow was a self-inflicted wound. On 18 January 1918, a terrible fire broke out at Ahlhorn, the main Zeppelin base. Five Zeppelins were destroyed. An assistant mechanic recalled the destruction: ‘I heard the benzine tanks explode, the flames crackle, the girders break and the glass burst.’ Next morning, he surveyed the damage: ‘I saw the lean iron ribs of several sheds standing out like leafless trees in the wintry sky. Ahlhorn had simply been wiped off the earth.’

The last attack on London was on 19 October 1917; only one Zeppelin, L45, got through. The Midlands, the north and East Anglia suffered four attacks during 1918. Wigan bore the brunt of a five-Zeppelin assault on 12–13 April. The local paper reported the death of a woman in her bed: ‘a fragment of the bomb or splinter shot across the room, cut away her face and killed her instantly’. The final attempt was made on 5 August 1918. Returning empty-handed due to bad weather, Paul Strasser, the leader of the naval Zeppelin fleet, and his ship, L70, were consigned to a watery grave.

Over the course of the campaign, there had been nearly 80 raids – 26 of them on London – causing 557 deaths. Had the German incendiaries been more efficient, the toll would have been much higher. As it was, Britain was faced with a new menace, the Gotha bombers, conventional planes that threatened even more havoc. Unfortunately, the codebreakers were unable to predict their arrival, as they only used wireless on take-off, thereafter maintaining radio silence.

The first major assault came on 4 July 1917. The authorities reacted quickly, setting up a body called the Air Organisation and Home Defence Against Air Raids under the leadership of the dynamic South African Jan Smuts. It introduced a 45-minute early-warning system, linked to 80 fire stations within a 20-mile radius of Charing Cross. During eight days in late September, known as the Blitz of the Harvest Moon, the Gothas dropped 5,000 kg of bombs, killing 69 people. Nearly one million Londoners sheltered in the Underground. Others slept in parks and fields or simply left the capital. But the air force’s improved armaments inflicted mounting losses on the Gothas, which at this late stage in the war the Germans could not afford to sustain, and the raids slowly petered out. Overall, through trial and error, invaluable lessons had been learned that could be applied next time Britain faced death from the skies.

In the early 1930s, Blinker Hall, with the help of a ghost writer, embarked on his autobiography. In the few chapters that survive from this unpublished work – it was killed stone dead by the authorities – Hall claimed that under his guidance, naval intelligence ‘grew … into an almost worldwide organisation with a multitude of the most diverse activities’. This was no idle boast. His power and influence spread far and wide; nothing was out of bounds. Any action he thought would help bring victory was legitimate. He didn’t care about ignoring the chain of command or stepping on other people’s toes. Nor did he mind if his actions were morally or legally dubious, or carried considerable risks; as he put it, ‘I came to the decision that if we were to get on with our job, there must be no slavish regard for peacetime precedents.’

Almost immediately he proved true to his word. The issue he addressed head on was that of postal interception: the opening of suspect mail. In 1911, when Churchill was Home Secretary, the system was very limited: a warrant had to be obtained for each single letter or telegram that the security services wanted a peek at. Churchill adjusted the law so that warrants covered all the mail received by suspicious individuals.

Nevertheless, in autumn 1914, there was only one censor at London’s Mount Pleasant sorting office, and a few overwhelmed staff. One clerk admitted that only 5 per cent of the post was being dealt with, the rest piling up in cupboards. Once Hall was made aware of the situation, he felt ‘it was imperative to enlarge very considerably the existing scope of censorship and to press for its rapid extension’.

He paid a visit to the man in charge and told him he wanted ‘to make sure that
all
the foreign mails are opened and that no secret message gets through’. Without bothering to ask for permission, he got hold of 200 men, all volunteers from the National Service League, squeezed £1,600 from Churchill on false pretences, and put these resources to work on a two-month trial basis. He quickly realised that the Germans were ordering contraband goods via the post, thereby defying the blockade.