The Wrens of WATU, or How Women Wargamers Helped Win World War II

I originally wrote this story as a twitter thread over three years ago. I am resurfacing it now (submarine pun intended) as May 6th is the 80th anniversary of the turning point in the Battle of the Atlantic, and there is a special event coming up on that date that you may want to attend if you are near Liverpool. More on that at the end of this post.

In early 1942 many of the Allied naval forces were being diverted to the Pacific, and the German U-Boats were becoming increasingly deadly.

The British navy appointed Captain Gilbert Roberts, who had been sidelined due to tuberculosis, to head up a small team called the Western Approaches Tactical Unit, or WATU. Their mission – figure out new tactics to regain the upper hand over the U Boats.

Roberts was a big proponent of using war games to discover new tactics, but was disappointed when he arrived in Liverpool to head up the team, as it seemed admiralty interest had already waned.

He received a primitive room with a few tables, and his team was mostly comprised of young women from the Women’s Royal Navy Service – also known as Wrens.

Wrens were a supplementary service for the Navy that provided support services like cooking and repair. 4 Wren officers (Elizabeth Drake, Jane Howes, Jean Laidlaw, and Nan Wailes) and 4 privates (only name I could find is Janet Okell, who was only 17 at the time) were assigned.

They were all thrilled to be doing “serious work”.

Roberts trained the Wrens in ASW (anti-submarine warfare) techniques and technology and found them all to be quick learners. They rapidly mastered the material and dove into running the wargames that were to change the face of the battle of the Atlantic.

The wargames were conducted in the sole WATU room by drawing chalk outlines on the floor showing ship and sub locations and paths. The convoy commanders viewed the room through a screen so they couldn’t see the chalk outlines.

The first games showed that the tactics the commanders thought the U boats were using couldn’t be right. The wargamed results of those tactics didn’t match what was happening in the actual battles.

The Wrens realized that rather than attacking from outside the convoy, as was assumed, the subs would position themselves along the path of the convoy, wait until it passed over them, and then attack from the stern.

Wargaming furiously, the Wrens developed a new tactic that would counteract the German approach. Jean Laidlaw called it “The Raspberry” because that’s what she wanted to give to Hitler.

A skeptical Admiral Percy Nobel came in for a demonstration, but his demeanor changed as the game unfolded and he saw the utility of The Raspberry. He immediately sent it out to the fleets and Roberts (but not the Wrens of course) got a promotion on the spot.

“The Raspberry” worked fantastically out in the field, and WATU set up a course to train naval officers. Over 5,000 attended the school and were instructed by the Wrens in new ASW techniques. They proved extremely skilled in teaching the officers without “hurting their feelings”.

As Raspberry worked at sea, the Germans changed their tactics, but WATU was ahead of them, anticipating their changes and developed Strawberry, Gooseberry, and Pineapple as reactions that allowed the Allies keep the upper hand.

However later in 1942 the Germans amplified their use of wolf packs – large groups of submarines working in concert, which were proving to be very dangerous. But the Wrens realized that they must rely on radio communications to coordinate, and that was a potential weak point.

The team developed a new tactic called Beta Search that would trick the subs into thinking it was safe to surface and use their radios, but the escorts would then dash towards them and sink them.

In November 1942 Sir Max Horton, Commander-in-Chief of the convoys came to WATU for the first time to learn about the new tactic. The admiral was assigned to play the sub commander and Janet Okell (now 18) played the escort group commander, using Beta Search.

Horton was a bit surprised and miffed at being put up against the young woman, and it caused a bit of controversy, but she had demonstrated an instinctive grasp of ASW and U-Boat tactics.

He played the game 5 times to attempt to evade the escorts, and each time Okell relentlessly closed in and sank his U Boat. Horton was a skilled submariner, but the new tactics flummoxed him. Often the first clue he got that Okell had found him was that he was being depth-charged.

He even insisted on checking the screens to see what the escort commander could see, but everything was legit. Horton was reportedly “horrified” that he had been schooled by the 18-year old Wren, but unlike many he was able to put his ego aside and Beta Search was sent out.

The HMS Vidette was the first to try it out and it worked flawlessly. The Vidette sank a U Boat immediately.

The wargames at WATU became more influential and popular with officers, and eventually even King George VI took the course. And tactics continued to change and evolve, and the Wrens led the way. By the end of the war WATU had eight male officers and thirty-six Wrens.

Postscript

On May 6th, 2023 at the Western Approaches HQ Museum in Liverpool, there will be a special event commemorating the 80th anniversary of the tide turning in the Battle of the Atlantic. At the event you will be able to:

• Celebrate the remarkable achievements of the WATU Wrens!

• Chat with the direct descendants of WATU about careers in professional wargaming: yes, you can get paid to play board/war/computer games for a living

• See the WATU game in action, send some signals to the convoy if you’d like.

• Explore the Western Approaches Museum, including their new Wrens exhibition, Leading Wren Helen Coop’s WATU scrapbook, and bits from their newly-acquired U-Boat.

• Delight in a Derby House Principles wargame being played in the actual Derby House that the principles are named for. 

More details about this and past similar events available here, courtesy of the fine folks at PAXSims.

Post-Postscript

Much of the material in this story is adapted from this article .

If you are interested in learning more about the Wrens, check out the book A Game of Birds and Wolves by Simon Parkin.