Death Ray (32 page)

Because of their work, by the time war broke out Britain had a defensive chain of coastal radar stations providing our fighter squadrons with a vital early warning system. Had we not had radar, maybe the outcome of the Battle of Britain would have been different, and maybe Hitler would have given the green light for Operation Sealion, the full-scale invasion of
Britain!

The Nazis developed radar too, but their version appeared different and so the British set out to discover how it worked. It resulted in one of the most daring raids of the war. During the night of 27–28 February 1942 British paratroopers landed close to the coast of Normandy and a village called Bruneval. They fought their way to the tall cliffs, and the location of a German radar station comprising the Giant Würzburg and Freya installations which lay at the heart of the enemy’s defences. Under fire, they dismantled the equipment and carried the pieces down the cliffs to waiting landing craft belonging to the Royal Navy. The mission, codenamed Operation Biting, was hugely successful. The local French Resistance also played their part, providing important information about the strength of German forces and the extent of defensive positions. Capturing this vital equipment led to a method of radar jamming being perfected, thus protecting the pilots and aircraft of Bomber Command. This amazing true story inspired
Special Operations: Death Ray
.

Eventually, aircraft were fitted with a form of radar as well, enabling pilots to detect the enemy at night and in thick cloud. A vital component in this system was the magnetron. You may not have heard of a magnetron before but it is very likely that you have one at home – in your kitchen – because a magnetron is also used to generate the microwaves in your microwave oven!

Although
Death Ray
is a work of fiction, Finn Gunnersen’s clandestine world of Special Operations is
also
firmly rooted in real events. A dozen houses in the beautiful New Forest in southern England were requisitioned during the war and, along with other locations, including Arisaig in the Scottish Highlands, formed part of a training school for secret agents. The organization was called the Special Operations Executive (SOE). In total secrecy about three thousand men and women of more than fifteen different nationalities passed through the school during the course of the war. Many were subsequently sent behind enemy lines on dangerous missions. Most of these volunteers were ordinary people, not highly trained military personnel. The heroism and sacrifice of numerous agents is well documented and we owe them a great debt of gratitude for the work they did. The training Finn and his friends received at Mulberry House and at Arisaig has been based on true accounts of the skills taught to agents at the time. Lying on the foot plate and rolling off really was considered the safest way of getting off a fast-moving train! Of course, it is so dangerous that it’s not something that should ever be attempted. Unless, that is, your country is at war and you are running for your life!

In the early years of the Second World War both the SIS and the SOE used the same method of enciphering their Morse-code messages. Each agent was given a unique keyword or phrase to memorize. It was a closely guarded secret. In
Death Ray
Finn’s key phrase was:
On a dark and stormy night
. The Playfair code worked as follows:

The first thing Finn did was write out his key phrase in lines of five letters, each line directly underneath the previous one, to form the beginnings of a grid. Importantly, no letter gets repeated, so, for example, although the letter O appears twice in his key phrase it only appears once in the grid.

So Finn’s grid looked like this:

Finn then added all the unused letters of the alphabet in the right order to complete a 5 x 5 grid. As the alphabet contains 26 letters and only 25 are needed, the letters I and J are both treated as I. This is what Finn’s completed grid looked like:

The message Finn sent to London in
Death Ray
was:

URGENT … ODETTE ARRESTED … WILL TRY RESCUE … SUSPECT JACQUES IS ENEMY SPY … DEATH RAY COMPROMISED … ADVISE NEXT STEPS

Finn divided his message into pairs of letters (called bigrams):

UR … GE … NT … OD … ET … TE … etc.

Taking each pair in turn, Finn located their positions in his grid. So, for the first pair, ‘UR’, their positions are:

Now comes the clever bit! Finn had to think of these letters forming the opposite corners of a square or rectangle (in this case the square,
ORUZ
). He then wrote down the opposite corners to
UR
– that is,
OZ
. These are the letters he transmitted to London (there they’d do the operation in reverse to decode it).

If you try out the Playfair code, you will soon discover several complications. Quite often pairs of letters fall in the same row or column and hence don’t form a square or rectangle. For example, the fourth pair of letters (or fourth
bigram
) in Finn’s message is
OD
; both letters are in the top row of his grid. Finn would get round this by shifting the second letter one space (either left or right,
or
up or down). In the case of
OD
, Finn would shift down. So the pair
OD
becomes
OM
, enabling him to form the rectangle
ODKM
. Taking the opposite corners, he can now code
OD
as
DK
. Worse still, sometimes he would be faced with coding an identical pair of letters, for example
DD
. To make a square out of these Finn would have to shift the second letter in both directions; that is,
diagonally
– so
DD
would become
DY
, thus creating the square
DRMY
. His coded letters for
DD
would thus be
RM
.

These complications can make decoding a message quite a challenge because the person receiving Finn’s message doesn’t know that he’s had to make the above adjustments. So they would simply decode each pair of letters and try to form proper words from them. What would look like bad spelling mistakes would alert them and they’d then try out various options until the message made sense.

As you can imagine, coding and decoding was a hard task for an agent working in the field, demanding great concentration and attention to detail while always fearing possible discovery and arrest. Try and see if you can work out the rest of the coding. Then imagine you’ve received the message and have a go at decoding it using the same approach, or invent your own key phrase and grid.

The Playfair code was extremely hard for the enemy to break, although it had one major drawback. If captured, an agent might reveal his key phrase under interrogation. The enemy could then use it to send false messages.
A
series of ‘security checks’ were often included, e.g. deliberate mistakes – their presence or absence alerting London that the agent had probably been compromised. Eventually the SOE developed its own coding methods, including what were called
WOCs
(Worked Out Codes) printed on silk. The agent could easily destroy them if he or she feared capture, and with no secret key to remember, there was nothing the agent could divulge under interrogation. These later evolved into what were called
One Time Pads
, in which a
WOC
was used just once and then destroyed.

Finn has sent you an urgent message. Can you decode it?

TIPS
:

1. First use the above grid to decode each pair of letters in turn and write your answers in the boxes below, underneath Finn’s coded version. The first pair is tricky to fully decode so I’ve got you started and helped you out by solving the three other really difficult pairs
.

2. Now look at your results and see if you can read the message. If you can’t, it is because one or more of your pairs needs to be reversed (there are two ways of writing down each pair). For example, when you decode Finn’s second pair, FU, you will find that it forms the square EFUV. You can write down the opposite corners as either EV or VE. You can’t be sure which is correct until you try and read the message. So work along your decoding from left to right, and see if by switching round your pairs of letters you can make sense of the message
.

Good luck
.

(Note: Those I’ve already solved for you are in the right order.)

3. Still having problems? Hint: Finn’s message contains five words (4, 3, 4, 8 and 3 letters respectively)
.