The Girls Who Beat the Germans: How Chalk, War Games, and Wit Helped Win the Battle of the Atlantic

It’s easy to overlook the quiet heroes of war:

The people behind the scenes who never fired a shot.

They out-smarted the enemy, rewrote the rulebook, and helped win one of the longest, hardest battles of World War II.

And they did it armed with nothing more than intellect, data, and chalk.

By 1941, Britain was in real trouble.

WWII was only two years old but the country depended on imports for 70% of its food and 95% of its fuel.

It was called the Battle of the Atlantic.

If Britain ran out of food, they’d have no choice but to surrender.

The British took to grouping merchant vessels together in a convoy and protecting them with warships. That didn’t help, and no one knew why.All that was known was the German U-boats attacked at night, and submerged before the British warships could respond. Something had to be done.

Captain Gilbert Roberts was a Royal Navy officer placed on shore duty while he recovered from tuberculosis.

He called it the Western Approaches Tactical Unit (WATU). Its home was a set of rooms in Liverpool.

Before he left London, he was sent into a meeting. There, Churchill himself told him, “Find out what is happening, and sink the U-boats.”

The group he led wasn’t made up of experienced sailors or officers. Those men were off fighting the war.

Instead, he had been given a staff of mathematicians, linguists, and statisticians from the Women’s Royal Naval Service, or WRENS. Like the boys had been shipped to battlefields, some of these women were girls just out of school.

They learned fast, mastering anti-submarine tools and terminology. Some already spoke German, as did Roberts, and were able to translate U-boat manuals. More importantly, they interviewed survivors of the U-boat attacks:

And were able to plot the events using chalk and wooden ship models on the floor.

Roberts and his team reconstructed the attacks on the game board, and tried to see patterns.

They were surprised to find that some U-boats were not attacking from outside the convoy as the Royal Navy’s escort commanders assumed — because that’s what the Germans did in the First World War. Instead, the submarines were sneaking into the middle of the convoys at night on the surface — so they could use their fast diesel engines and look like other convoy ships on radar — and firing at close range from inside the formation. 

Those attacks in the dark from within the convoy explained why there were such heavy losses.

The other finding was that the escort ships adhered to rigid command procedures.

If a sonar operator detected a possible U-boat, the escort’s captain couldn’t act immediately. Instead, the contact had to be confirmed, reported up the chain of command, and approved before any attack was made. This bureaucratic delay could take minutes — long enough for a U-boat to fire its torpedoes and submerge. WATU’s wargames repeatedly showed how deadly this delay was. 

It wasn’t the first time that British military protocol got in the way of success. 

When Germany invaded Poland in 1939, Polish fighter pilots took to the air in obsolete aircraft against impossible odds.

Many escaped through France and fought again during the brief campaign there in 1940. After France fell, they fled to Britain. 

The Poles spoke little English, had fierce tempers, and flew with a style the British considered reckless. At first, the RAF wanted them to retrain from scratch.

The pilots objected. They had combat experience, they didn’t want or need lectures. Finally, after some bureaucratic wrangling, Squadron 303 was formed in July 1940.

The British system relied heavily on formation flying — the “Vic” formation, a tight triangle of three planes.

It forced pilots to focus more on keeping position than spotting enemies, and it made the whole group an easy target. The Poles thought it was nonsense.

Squadron 303 flew in looser, more fluid groupings, allowing each pilot to maneuver freely and attack as opportunity arose.

The RAF worried they were undisciplined, but they couldn’t argue with the results.

In just six weeks of combat during the Battle of Britain, Squadron 303 shot down 126 enemy aircraft, more than any other unit in the RAF, and with fewer losses than most. When British officers asked how they achieved such results, the Poles said they fought to win, not to follow rules.

When WATU discovered that protocol was delaying response time, they used their wargames to develop a new one.

A 21-year-old WREN, statistical analyst Jean Laidlaw, named the operation “Raspberry,” as in blowing a raspberry at Hitler. It worked like this:

When a merchant ship in the convoy was hit or a close torpedo wake was sighted, anyone of any rank could immediately start the procedure — there was no need to wait for an order from the top. The escort would launch two white rockets and announce the code word “raspberry” over the radio.

Escorts on the rear and flanks converged on the convoy, and would then turn outwards and do long outward sweeps away from the convoy, firing star shells and using sonar/radar to search the surface for a U-boat for about ten minutes. Then they turned and swept back to their starting positions — effectively combing the entire perimeter and blocking easy escape routes. 

The combined converging-then-sweeping movement forced a surfaced U-boat either to stay surfaced and be attacked, or to dive, losing the speed advantage and facing depth charges.

Unlike the earlier single-direction sweep tactic, Raspberry had all escorts participate, removing delay and blind spots.

Raspberry was tested repeatedly on the WATU game floor, but the naval brass didn’t want to accept the idea.

Admiral Sir Max Horton, a hero submariner, was commander-in-chief of the Western Approaches.

Horton visited WATU, even though he thought it was a waste of time, and was challenged to play ‘The Game,’ as they had nicknamed it. He would play the U-boat commander fighting against someone standing behind a canvas screen with only a few holes cut in it. The screen limited what his opponent could see, just as the convoys were blinded by night.

Five games were played.
Horton lost all five of his U-boats.

He accused Roberts of rigging The Game and was infuriated when his opponent stepped from behind the canvas.

She was 20 and had never been on a boat.

Horton had been beaten by a girl. He put WATU’s recommendations into effect.

Through the summer of 1942, U-boats had been hitting as many as 146 ships a month.

Once WATU trained convoy personnel on their new tactics in early 1943, things changed quickly. By May, the number of ships hit had dropped to 49, and by June 1943 it was 27.

In that same May, the Germans lost 43 U-boats, their worst losses of the war.

German Admiral Karl Dönitz recognized the defeat and ordered his submarines to withdraw from the North Atlantic entirely. They gave up.

The turnaround took less than a year. It began on the WATU game floor, where WRENS with chalk and model ships rewrote the rules. Squadron 303 rewrote their rules, too.

However, the people who do the work rarely get the credit.

The accolades go to the commanders who had to be convinced that girls and rogues were on to something. Some of the WRENS’ work remained classified until recently.

But their names:

— deserve to stand beside those of the admirals and captains they once trained.

The book Dywizjon 303 (Polish for “Squadron 303”) by Arkady Fiedler fictionalized the pilots’ names for their security.

Not all rules need to be rewritten.

But they always, always, need to be questioned. 

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