A Game of Birds and Wolves: The Ingenious Young Women Whose Secret Board Game Helped Win World War II

by Simon Parkin

On the surface and while travelling at ten knots the most common U-boat model of the time, the Type VII-C, had a range of nearly 8,000 miles. With six weeks’ worth of fuel, a single U-boat could roam the entire Atlantic span, from the panoramic beaches of France to the crags of the North American coastline. The radius of the war now spanned the ocean. There was no longer a safe spot where the convoy flock would be free from trouble. The gap had been closed.

Of all the various forces and divisions of air, land or sea, on both sides of the conflict, the U-boat posting had the greatest mortality rate of any in the Second World War. British planes dropped leaflets over Germany, warning potential new recruits that for every one of the 2,000 U-boatmen who were currently living as prisoners of war in Britain, five more had already been killed at sea. Life-insurance companies in neutral countries estimated the average life of a U-boat sailor to be fifty days.7 This was not the hyperbole

of propaganda. Of the 39,000 men who went to sea in U-boats during the Second World War, seventy per cent were killed in action. By contrast, only six per cent of those who fought in the British Army died in combat.8 In the early 1940s you were more likely to die on a U-boat than on any other mode of transport in existence.

By the end of the war U-48 would have distinguished itself as the deadliest U-boat in Hitler’s submarine fleet, sinking no fewer than fifty-five ships before her maintenance crew, aware that the war was at an end, scuttled her. In September 1940, however, she was almost new and untested. Just below the smell of diesel, a talented sniffer could still pick out the fading aroma of fresh paint. Like Bleichrodt, who commanded in the shadow of Germany’s trio of celebrity U-boat aces, Otto Kretschmer, Günther Prien and Joachim Schepke, U-48 still had everything to prove.

There were, at that time, around 1,500 of these contraceptives on board.11 They were not intended for the men’s use at sea, but rather to be filled with helium, tied to the submerged U-boat and extended up, through the water, into the air, where they could be used as weather balloons or, even more usefully, as antennae extensions, enabling U48’s wireless radio to be used underwater to make contact with base. Once any messages had been sent and received, the tether would be cut, and the condom would fly up and away.

To enact his plan, on 1st August 1940, at Doenitz’s urging, the German naval high command authorised a total blockade of Britain, giving U-boat commanders the mandate to attack ships without warning or prior approval from superiors. Five years earlier Germany had signed a protocol barring this kind of unrestricted use of submarines as weapons of war, but the outbreak of war had, in Hitler’s view, nullified the agreement. International shipping law prohibited attacks on merchant ships, but Doenitz’s blunt battle orders that ‘fighting methods will never fail to be used merely because some international law forbids them’ made their commander’s position clear to every subordinate.

After the map was folded up and the pieces packed away, Doenitz wrote a report describing what had happened. The Blue team’s failure, he surmised, lay not in any particular tactical mistakes but in the ‘emptiness of the sea’, as he put it. The German fleet was simply spread too thinly. None of this was surprising to Doenitz, who, since becoming the head of the U-boat division in 1935, had been urging his superiors to build more–and better–U-boats. But the game provided evidence to support his arguments. In his written summary, Doenitz drew the conclusion the Germans would require ‘at least some three hundred’ operational U-boats if they were to form the wolfpacks needed to sink the numbers of Allied convoy ships required to starve the British.

A few months later, in May 1939, Doenitz restaged the Red vs Blue training exercise, this time transposing the scenario from the board to the ocean.15 In the Bay of Biscay, off the coast of Portugal, he summoned fifteen U-boats to comprise the Blue team’s fleet. The Red team, playing as the British, consisted of two helpless merchant supply vessels and two well-armed escort ships, the Saar and the Erwin Wasser. This game was intended to be played out on the entire expanse of the sea. Nevertheless, after just four hours one of the U-boats spotted the pretend ‘convoy’. Doenitz watched while, as the hours passed, the U-boats congregated and tracked the convoy, first in a group of seven then, by the end of the game, in a pack consisting of no fewer than thirteen boats. Doenitz’s conclusion was foregone. In his report, he wrote that success against the enemy could only be achieved when ‘a great number of U-boats can be successfully set on the convoy’. Both the game played on the water and the game played on the board had proven the effectiveness of his tactic.

While it made sense that coordinated assaults would be more effective than lone-wolf attacks, there was an equally logical concern that the radio signals necessary to organise the U-boats into a pack could, if intercepted by British technology, forfeit any element of surprise and aid detection of the vessels by the enemy. Moreover, Grand Admiral Raeder, commander-in-chief of the German navy, wanted to invest in a surface fleet of warships to rival that of the Royal Navy, and diverted funds away from the U-boat construction plan toward surface vessels. Finally, Hermann Goering, Hitler’s closest ally and confidant, a former First World War fighter-pilot ace, favoured the Luftwaffe, not only because of personal bias but also because planes could be built more quickly than U-boats and, therefore, could be seen to be having a more immediate effect.

This kind of bold attack from within the columns of a convoy, while new to the Battle of the Atlantic, had precedent. Doenitz, who had seen first-hand its effectiveness working under Forstmann, had managed–or at least, not wanting to be shown up by his young captains, claimed to have managed–on more than one occasion to pass undetected through the prowling escorts, into the columns of the merchant vessels to mount attacks.

In fact, the Royal Navy’s anti-submarine tactics were, in the early stages of the war, miserably ineffectual. The British ships had no radar, and only a few were equipped with ASDIC. This formative submarine-detection device was housed in a dome beneath the hull of escort ships, like a great polyp. It sent out pulses of sound waves, which emitted a ‘ping’ that would produce an antiphonic ‘tong’ response if and when it struck a solid object within a 3,000-metre radius. This call and response would provide an accurate range and bearing. It was, however, notoriously unreliable in its formative iterations, upset by differing density layers in the water, and would fail altogether if the ship exceeded eighteen knots. Moreover, hardly anyone knew how to work the system properly. One operator described operating ASDIC as like playing the harp, a skill that required dexterity and endurance, and of which those assigned to it had no experience.

immediately distinguished itself as the first German submarine to cross the Atlantic. In its maiden voyage in 1916, it carried $1.5 million worth of gemstones, valuable dyes and pharmaceutical drugs from Europe to Baltimore (much to the protestations of the panicky British, who beseeched the Americans not to classify U-boats as merchant ships, arguing that submergible vessels cannot be easily stopped and searched for illicit munitions).

The Deutschland was one of a hundred or so German U-boats that were towed to England at the end of the First World War to be

scrapped for metal, and the reliable, German-made diesel engines removed and used in industrial factories.

The attack, in which 117 passengers and crew members died, violated the Hague convention, which prohibited attacks on unarmed passenger vessels, and ensured that the start of war was marked by national awareness of the lethal U-boats stalking British shipping lanes.

In a speech at Mansion House on 20th January 1940, at a moment when British forces had sunk just nine of Germany’s fifty-seven U-boats, Churchill claimed to have sunk ‘half the U-boats with which Germany began the war’. To arrive at this dishonest conclusion, Churchill had added sixteen U-boats that the Admiralty believed may have been sunk to the nine U-boats known to have been sunk. To this number, for good measure, Churchill also added a further ten U-boats of his own imagining, to bring the total to more than half of the U-boat fleet as British intelligence understood it to be. This exaggeration of gains and suppression of losses, be it by accident or scheme, had, as the author of a classified inquiry into publicity around the Battle of the Atlantic wrote

immediately after the war, ‘a heartening effect on the British public’. The political advantage apparently justified the damage caused to truth.5 Arguably, had the full miserable extent of the Allied performance in the Battle of the Atlantic to date been fully known, it may have had an invigorating effect on the coordination of efforts to find an urgent solution. The author of the inquiry, Admiral V. Lt. Godfrey* concluded, however, that Britain ‘never came quite clean about the progress of the war at sea’.

In the five months from June to October 1940, during which the City of Benares was lost, U-boats sank 274 merchant ships and sustained just two losses. By the end of the year the U-boats had sunk more than 1,200 ships, about five years’ worth of construction work in typical peacetime conditions, and more than the rest of the German navy and Luftwaffe combined.

Point nine, however, went against the written advice that U-boat captains maintain a minimum distance of 1,000 metres between the U-boat and its target. Kretschmer countered, plainly, that at every given opportunity, torpedoes should be fired at extreme close range. ‘This can only be done’, he wrote, ‘by penetrating the escort’s anti-submarine screen and, at times, getting inside the convoy lanes.’ Having scored three kills in quick succession, Kretschmer knew that there was no more efficient way to cause havoc on a British convoy, causing the escort captains to flounder. ‘This should be the objective of all our attacks,’ he added.

On graduating, she was sent to Scarborough where, as the war continued, more and more Wrens would congregate in a secret underground hall on Irton Moor, today inhabited by Government Communications Head-quarters (GCHQ), intercepting and decoding U-boat radio signals.* For all the wolfpack’s power and menace, it had one key weakness. In order to organise their U-boats for an attack, the captains needed to communicate at regular intervals, initially to report the sighting of a convoy, and then to invite other boats to join. Even in the midst of battle, requests often came in for U-boats to announce the result of specific attacks, fuel and torpedo stocks and, thanks to those helium-filled condoms, to issue weather reports. These signals, when picked up by Allied shore stations, acted as clues to the U-boats’ whereabouts.

By triangulating the signal from two sources, a fairly accurate location could be determined, and the estimated position of the U-boat pinned to the plotting maps around the navy’s various premises.

There was one notable exception to the rule. Occasionally, after a fortnight’s cavorting while on leave in the French ports, news would arrive via the U-boat’s radio that one of the crew had got a girl pregnant. The man would be expected to ask the woman to marry him. The U-boat’s patrol, however, could not be interrupted or cut short. As such, the exchange of wedding vows would be organised remotely, over the radio.

For all of war’s great horrors, service in the Wrens offered these women an unexpected freedom from the strictures of their previous lives, where they were subject to the rules of their Victorian fathers. For many young men the Second World War wiped out a multitude of possibilities. For many young women, however, war obliterated previously impenetrable barriers. In assuming an active role in the war effort, Wrens slipped the expectation to marry early, remain at home and bear children at the earliest opportunity. Joining the Wrens was something akin to setting off for university, a profound loosening of the centuries-old constriction of female prospects. For these girls–and many were still girls–war’s secondary effects had to do with liberation, excitement and possibility.

Technology has a distancing effect on combat. The fist becomes a sword. The sword becomes an arrow. The arrow becomes a trebuchet. The trebuchet becomes a torpedo. The torpedo becomes a nuclear missile. The ICBM becomes, maybe, a clandestine social media

campaign, designed to undermine and topple democracies. With each step change the attacker is removed yet farther from the material effects of his actions. At a distance it is harder to properly count the cost. It is, surely, our obligation to count the cost.

Exactly three weeks after the sinking of the Aguila, Winston Churchill, who had replaced Neville Chamberlain as prime minister the previous year, addressed Parliament to announce that the government would no longer be playing by the rules of the German’s so-called tonnage game. The publication of official monthly figures reporting shipping losses to U-boats would cease. To justify the information blackout, Churchill argued ‘it is not desirable to give [the enemy] too precise or, above all, too early information of the success or failure of each of his various manoeuvres’. He added, for reassurance, ‘the public, and indeed the whole world,

have however derived the impression that things have gone much better… I cannot deny that this is so.’

parents, sent his son to America as an evacuee), to discontinue the publication of monthly losses was not only motivated to hide this information from the Germans, but also to hide it from the British people.

The British diet had been forced to move away from fat-rich foods, which made up thirty-eight per cent of the average calorie intake pre-war,24 to a carbohydrate-rich diet of wholemeal bread and potatoes. The shift not only flattened the variety and taste of the typical Briton’s diet, it also had negative practical consequences. For a manual worker to obtain the 4,000 calories they needed for a day’s work from carbohydrates

alone, they would have to spend almost the entire day eating. Fatigue became widespread in the workforce.

He knew that the Germans preferred to attack at night, using daylight hours to shadow their prey. He knew that U-boat captains preferred to attack from the bow of the convoy, before falling back to fire torpedoes on the convoy’s beam, finally withdrawing to a safe distance to reload the tubes. He did not yet know, however, about the technique pioneered by Kretschmer, of attacking from within the perimeter of the convoy, at point-blank distance.

Roberts wrote of the incident in the plain, pragmatic prose of the wizened sailor, who sees in the sparkling ocean not serenity, but a sleeping monster.

The use of games to represent the manoeuvres of warriors on stylised boards can be found throughout the historical record; archaeologists have unearthed sets of miniature soldiers that represent Sumerian and Egyptian armies. Many of the earliest board games that, like chess and go, are still played today are either military-themed, or explore military concepts of strategy and tactics. Games establish consequence-free realities in which we can explore and experience situations that in actuality are too dangerous, rarefied or consequential. This makes them the ideal sphere in which to experience war.

Chance played its role in Roberts’ games at Portsmouth, which, on a board painted across the entire floor of a room, on which ships of various sizes were manoeuvred, bore a passing resemblance to Battleship, but the aim was to reduce serendipity’s role in sea battle by incrementally refining naval tactics.

(In fact, a wargame to test convoy protection was designed and played at the naval college in Greenwich in January 1938. This game, of which Roberts was seemingly unaware, correctly estimated the time of war’s outbreak but assumed that the threat to convoy ships would come not from U-boats, but from German raiders disguised as merchant vessels.19)

The bomb wedged in the concrete outside Roberts’ front door, smoke curling from its fuse, was one of the latest yet most unreliable weapons in the Luftwaffe’s arsenal. A bloated incendiary device, the oil bomb was known to the Germans as the Flam or Flammenbombe and

contained an oil mixture and a high-explosive bursting charge. Many of the forty-two oil bombs that were dropped during the Blitz on the borough of Kensington and Chelsea, where Roberts was staying, failed to detonate, splitting the case open to spill gallons of fuel.6 As such, in January 1941, just a few months after its introduction, the Flam was withdrawn from widespread use.

During a Trade Protection committee meeting in autumn 1941, one member suggested the idea of a game that could be played aboard ships during training exercises, to simulate a U-boat sighting, and the ensuing cat-and-mouse hunt. A discussion followed on how a game might specifically improve the cooperation of the bridge team, from where a vessel is commanded by the ship’s captain, watchkeeper, lookout and pilot so that ‘the commanding officer and his anti-submarine control officer were left free to attack the submarine, and relieved of the necessity of attending to details such as the housing of the correct signal’.15 At a training facility in Londonderry, the development of a game with precisely this aim was already underway, led by Lieutenant Commander I. M. Carrs, an anti-submarine officer. By early September 1941, a few weeks after the sinking of the SS Aguila and its cargo of young Wrens, he had completed a prototype. His invention was designed to be played not on the floor, like those which Roberts had run prior to the war, but aboard an anchored ship. The crew would take their usual stations while

a U-boat sighting and attack was simulated. They would have to respond exactly as they would in a genuine U-boat encounter. The only difference was that the ship would remain stationary; the players would merely imagine it was moving around the water, with its position and the suspected position of the U-boat denoted by tokens on a map. In this way the captain and crew could picture the hunt in their imaginations, while using a ‘small device’ that worked much like a gyro compass, to help everyone envision what was happening at sea. The game would come with a box of pre-written orders that the commanding officer on the ship would need to follow, a celluloid protractor engraved with time distancer scales and various turning circles. Lastly, there would be a transparent sheet covered in lines and markings that acted as a ‘master plot’, to show how the hunt, ideally, should play out. This would be placed over the ship’s plot at the end of the game, to allow players to check how closely their actions correlated to the optimal course of action. The exercise was designed to test the commander’s tactical ability, as well as to expose any weaknesses in the crew’s capacity to work effectively together in the stress of battle. Unlike previous training exercises the pieces for the game would come in a box much like a board game, mass-produced and sent out to every escort ship in the navy. Its development,

Carrs’ commanding officer explained in a letter to the director of anti-submarine warfare at the Admiralty, would require the cooperation of various anti-submarine departments. In his letter, the CO requested the loan of young game designer Lieutenant M. E. Impey to join the project for a month from his current posting in Portsmouth, where Roberts was then working. Lastly, the captain wrote, ‘The Director of A/S Warfare is requested to obtain provisional approval for six gramophone records.’ Carrs’ and Impey’s game, it seemed, was to have audio accompaniment. A month later, on 15th October 1941, Impey flew from London-derry to Liverpool and on to London, arriving at the Admiralty the following day carrying under his arm a prototype of the game. After he outlined its workings, he explained that the gramophone record, which was to be played during the game, was needed to help increase the sense of realism for the ship’s crew. This was not to provide a stirring soundtrack, but rather the ‘ping’ and ‘tong’ of the ASDIC apparatus, the early form of sonar used to detect submarines, which would ...

boat would be almost imperceptible. Six days after Impey’s presentation, the game, plainly named ‘A Portable Anti-Submarine Trainer’, was green-lit for production. Three variants would be produced, one for destroyer crews, one for corvette crews and a third for trawlers, at a cost of £5 per set (not including the extra reels of paper rolls and traces that would be required for any subsequent play-throughs). Such was the expense of manufacturing the ASDIC gramophones that only a few select crews were issued with these. In all, fifty-two sets were made for destroyers, thirty-eight for corvettes and sixty for the trawlers, at a total cost of £750. Just as Doenitz had used games to prepare for the tactical and operational challenges of the U-boat war in the Atlantic, now games were being used to prepare the Allied crews hunting down those very same U-boats. Carrs’ and Impey’s game proved a useful resource, revealing snags and pitfalls in the consequence-free arena of play, so that they might be avoided in the consequence-rich arena of battle. But while ‘A Portable Anti-Submarine Trainer’ was ab...

unit. True effectiveness, as the wolfpack had so clearly demonstrated, required teamwork. And for that, a dif...

The truth was, Sir Charles Little told Roberts, that German U-boat losses had been gravely exaggerated, and Allied convoy losses equally downplayed. Next Little offered a glimmer of hope. Britain’s fortunes in the Atlantic, he said, were poised to change. The capture in May 1941 of an Enigma machine–one of the contraptions used by the Nazis to encode their communications–had hastened the breaking of the code that underpinned the cryptic messages that passed between U-boats at sea and Doenitz at his headquarters. Messages intercepted by Wrens in Scarborough were passed to Bletchley Park. There a staff of Wrens led by the genius cryptographer Alan Turing would decipher the U-boatmen’s

messages. Once translated, information was passed to the commander-in-chief of Western Approaches, who could then more intelligently direct his escort ships in the Atlantic either to avoid U-boats when in convoy, or to pursue them. Prior to the breaking of the Enigma code, the position of U-boats could only be added to the plots once they were spotted at sea; now the maps were pocked with U-boat markers, based on messages intercepted as they passed between Doenitz and his captains.

The depth charge was a rudimentary piece of technology, unchanged since its invention in 1917: a drum filled with explosives that was dropped over the side of a ship with a timer that could be pre-set to explode at a specified depth. It was an imprecise tool in a skirmish that required precision within three-dimensional space: the explosion needed to occur within twenty feet of a U-boat to have any effect on its intended target.*

Experienced U-boatmen would be able to listen to the smacking sound of a depth charge hitting the water and, based on the assumption that the bomb sank at a rate of four metres per second, use a stopwatch to calculate the depth-setting. Even if they got lucky, it was difficult for the navy to confirm a ‘kill’, although the smell of oil in the air and the sound of bubbling on the headphones implied success. If they could be spared, two escort ships would sit over the site of the suspected hit for forty-eight hours, a sufficient amount of time that, if the U-boat was merely playing dead, its air supply would run out, forcing the crew to resurface.

sketched drawing was taken from another man. This document was of a different category to the clippings. It showed the crude outline of a convoy with a U-boat attacking from within the columns, a hand-drawn illustration of the tactic that had sent so many people, and hundreds of thousands of tons of food and supplies, to the ocean bed. Here, depicted in a few lines, was the secret to the U-boats’ success.

One unassuming bullet point also mentioned the fact that U-99’s crew had been searched and, among their possessions, an illustration of the point-blank tactics pioneered by Kretschmer had been found. The importance of the document apparently evaded those who read the report. The revelation was neither noted nor communicated to the escort commanders. The three aces were gone, but their pioneering tactic remained in play. Roberts, when he arrived in Liverpool, would have to discover it for himself.

This was in addition to Derby House’s emergency generator, which was powered, with a flourish of cosmic irony, by a diesel engine taken from a German U-boat captured during the First World War.

This was Roberts’ masterstroke. By repeatedly playing through recent action at sea and using a game to understand the situation from all angles, he would be in a strong position to see where the British commanders had misunderstood the U-boats’ behaviour. The process would enable him to formulate the first universal set of defensive tactics for the navy to