After the fall of France in the early days of the Second World War Britain stood alone in her opposition to Germany in Europe. As an island nation she was vulnerable because food and materials for the war had to be brought across the Atlantic from America, running the gauntlet of German U-boats hunting in ‘Wolfpacks’. Britain needed more than 1 million tons of imports a week to survive so it was imperative to find ways to combat the U-boat threat in what was known as the Battle of the Atlantic.

Britain had prepared her sea defences based on the belief that Germany would fight a similar sea war to the one fought during World War I. No one had anticipated that France would fall so quickly thereby placing its ports on the western coast of Europe in the hands of Germany and enabling the Nazis to have a stranglehold on the Atlantic crossing. A new approach to the war at sea was needed.

‘War games’ have always been an important feature of military tactical planning and so the Western Approaches Tactical Unit (WATU) was set up in Liverpool led by Captain Gilbert Roberts under Sir Percy Noble who was made responsible for protecting convoys from the threat of German U-boats. Roberts brought together a group of officers and ratings from the Women’s Royal Navy Service (the Wrens) to ‘explore and evaluate new tactics and then to pass these on to escort captains in a dedicated ASW (Anti-Submarine Warfare) course’. Churchill’s instructions to the new unit were clear – “Find out what is happening in the Atlantic, find ways of getting the convoys through and sink the U-Boats!” The small staff under Roberts consisted of Chief Petty Officer Raynor, four Wren officers, and four Wren ratings, two of whom were only seventeen.

Roberts first analysed reports of attacks on convoys and came to the conclusion that only one Commander, F Walker, had any sort of tactic against the U-boats – he had set up a system whereby when the signal ‘Buttercup’ was given all escort ships under his command turned outwards and fired starburst shells to illuminate any German submarines on the surface. Robert’s analysis also led him to believe that rather than U-boats moving in to attack the perimeter of a convoy at night they were already amongst the supply ships and using their targets as cover!

The facility which housed WATU was very simple – a pattern of squares painted on the floor, some basic ships models, and a number of tactical tables. The first thing that the new team needed to do was to learn current ASW techniques and get an understanding of their technology before they began to create a set of rules so that they could play ‘real-time’ games where they responded to simulated naval attacks, developed tactics to combat them and analysed communications problems. The first problem they approached was the perceived tactic of U-boats hiding withing the convoys. By playing their war games they came to the conclusion that a U-boat would fire on the stern of a ship, dive and fall back behind the convoy, then surface again. To counter this they moved the escort back after an initial attack to sweep the area where the U-boats were expected to re-surface. This seemed to be a successful defence.

Sir Percy Noble thought that the plan for wargaming was unlikely to work, but after visiting WATU and watching the team at work he changed his mind. He observed a series of attacks on a convoy where the logic behind the assumptions made about U-boat movements were explained as were the tactics to combat these. Immensely impressed he gave his full support to ‘Operation Raspberry’ and ordered that all escort officers should attend the course.

Sir Max Horton (Western Approaches Command) attended one of the courses where he played the role of a U-boat captain. During the course he initiated five attacks on a convoy and each time his submarine was tracked and destroyed using the tactics derived from the war games. He was astonished that an eighteen year old Wren was able to outperform him so well and made sure that the new tactics were included in the next set of orders sent to the Fleet. King George VI was also impressed by the work coming out of Liverpool and visited WATU in November 1942.

After a time the unit adapted the training room so that the players who represented the commanders of the Allied convoy escort ships could only have a limited view of what was happening as would be the case in real life situations; only the umpires of the game were able to see the U-boat’s position. As each German tactic was countered and new ones introduced the war gamers of WATU came up with new counter-measures and Germany’s losses in the Atlantic grew. During the remainder of the war 5,000 officers attended the course, one of the very few military courses at the time which were run by women. By the end of the war WWATU had a complement of eight male officers as well as thirty six Wren officers and ratings.

At the end of 1943 Roberts was invested as a ‘Commanded of the British Empire’ for his work at WATU. He took a Wren Officer and a Wren Rating with him to Buckingham Palace for the investiture in recognition of the remarkable team of young women who played the war games which saved British shipping in the Battle of the Atlantic.