by Andrew Brown
Further data were obtained by an RAF sortie over the Normandy beaches by a single plane that was burning excess oil, so that from the ground it looked in trouble. It dropped its load of bombs causing craters in the beach that could be measured by subsequent aerial photography. As a bonus, one of the bombs landed in the sea and set off a pattern of plumes, suggesting explosions at a distance and indicating that the waters were heavily mined.60 To the alarm of Brancastrians, the RAF bombed their Norfolk beach for comparative purposes! In addition to supervising the large-scale tests at Brancaster, Bernal met representatives from Montgomery’s 21st Army group and briefed the American military about the beaches near the Cotentin peninsula. By the end of January, the reports on the Neptune beaches received final approval.61
With the basic topology of the beaches established, Sage now became more concerned with the waters of La Baie de la Seine. The Calvados and Bernières reefs had broken many hulls over the years, and the coastline had a fearsome reputation. As he began to look at charts, Sage realized that the main purpose of showing a rocky coastline was to warn sailors to stay away.62 The coastal chart that he was provided with by the Admiralty was based on the pilote francais chart of 1823. It had been reproduced by the Admiralty hydrographer in 1902, with additions and corrections in 1911. Bernal had the most up-to-date edition from March 1920.63 He now immersed himself in antiquarian maps and found that the earliest maps of this coast had been prepared on royal orders by ‘the great French hydrographer Beautemps Beaupré’64 in 1776. As he studied successive editions of the charts, Bernal noticed that errors seemed to creep in, and most seriously, submerged rocks present on Beaupré’s chart were omitted over time. It occurred to Sage that this was because the copyists were paid according to the number of charts they copied, not the number of rocks they plotted. During February and March, Bernal made frequent visits to Norfolk House, St James’ Square, the headquarters of the Chiefs of Staff Supreme Allied Command (COSSAC). There he worked on maps and liaised with the Theatre Intelligence Section (TIS), who were responsible for organizing and distributing intelligence needed for Overlord.
Just as the existing charts were unreliable, there were no up-to-date tide-tables available for Courseulles, for example. So Sage decided to generate his own. Soon after Dunkirk, advertisements had been placed in newspapers asking members of the public to send in postcards and snapshots of any seaside holidays they had spent in France. COHQ now obtained this collection of tens of thousands of pictures of the coast ‘from Calais to Nice’.65 Careful sorting left Bernal and his assistants with ‘an almost complete photographic record of Arromanches, taken from every angle’. Photographs with people in them, especially children paddling or wading, were very helpful in showing the depth of water at particular states of the tide, allowing some estimate of the beach gradient. The snapshot approach was reinforced with more systematic data obtained from aerial reconnaissance. Bernal explained why precise estimates of the gradient of the gently sloping beach and the tidal depths were vital.
If you take the fact that the slope of the beach was often as low as 1 part in 200, you can easily see that an error of even only five centimetres [in the depth of the tide] could mean an error of as much as ten metres along [up or down the slope of] the beach – and for beaches which are defended by mines and obstacles the precise point of [dis]embarkation can mean the vital difference, not only between life and death, but between victory and failure.
The tides, too, proved a way of measuring the depth of water down to lowwatermark. For deeper waters, of course, one had to rely on indications given by the refraction of the waves – a wave travels more slowly in shallow water, and by using appropriate formulae, it is possible from an air-photograph alone to calculate the depth of water.66
Bernal’s diary entry for 31st January, in addition to recording the final approval of reports on Neptune beaches, shows that he was preparing to brief the CCO on ‘Gooseberry’.67 Gooseberry was the codename given to the breakwaters to be created by blockships. Churchill had held a meeting the previous week when it was decided there would be a total of five Gooseberries, one in each divisional assault area, two of which would form the outer protection of Mulberry artificial harbours.68 Churchill had also called for a weekly committee, under his own chairmanship, to keep the preparations for Overlord under constant survey.69 The Bernal diary for 1st February records that he had been appointed to the ‘Attack on defended beaches’ sub-committee. It is clear that Sage was a key figure in planning Overlord – especially in defining the crucial subjects of the tides, shallows, shoals, beaches, cliffs and marshes. Although he lacked formal qualifications as an engineer, geologist or geographer, who but Sage would have had the ability to make sense of clues buried in mediaeval French literature, combine them with casual observations from nineteenth-century French natural scientists and from pre-war holiday-makers in order to produce lucid, predictive reports for the military that were backed by fresh empirical data?
It is not surprising in view of the intense and unremitting nature of the task he was undertaking that Bernal should be out ‘sick’ from 23rd to 27th March. He probably spent the time with Margaret Gardiner and Martin, who had returned to her house in Hampstead. She remembered that ‘Desmond was, rightly, very careful about what he told me. I remember at one point… I had decided that we were going to invade France. I had decided entirely on my own, and mentioned it to Desmond. He said, “You mustn’t say things like that, people will think I told you.” And he hadn’t told me, but I had deduced it myself from what was going on, what I knew. I remember that he was horrified when I mentioned this.’70
One of the lessons learned from the Dieppe raid was that exclusive reliance on vertical aerial photographs meant that vital details would be missed that might be visible on low-level oblique photographs. From mid-February, obstacles on the Arromanches beaches were identified by aerial reconnaissance. Their positions were plotted on 1/12,500 scale maps from vertical photos, with the identification of obstacle type being made from oblique photos. The number of mapped obstacles increased quickly as each successive sortie produced information at different states of the tide. More detailed 1/ 5000 scale maps were then produced showing the beach contour lines capable of being related directly to the position of the water line at any time of tide on any particular day. These maps also showed accurate beach profiles at frequent intervals along the beach and portions of rock outcrops and clay patches on the beaches.71 During the three months before D-Day, 200,000 sorties were flown over enemy-occupied territory,72 many simply to mislead the Germans about the Allies’ intended landing place, but the handful of photo-reconnaissance missions over the Normandy beaches provided information that prevented thousands of casualties.
The Bernal diary for April shows him concerned with underwater explosions, craters in beaches, surf, swell, weather, beach gradients, tides and underwater obstacles, beach obstacles, and beach mines.73 Small armed Combined Operations reconnaissance parties were sent to the Pas de Calais area in May. They found Teller [anti-tank] mines on stakes that would be detonated by any movement of the stake. This led to increased concern that earlier photographs from Arromanches were not detailed enough and might have missed this type of hazard. On 19th May, an RAF sortie flown at an altitude of just 50 feet gave precise identification and showed that a high percentage of the Arromanches beach obstacles were mined with Teller mines or adapted shells.74 While all the information was coming in on underwater mines, mines and shells on stakes, concrete tetrahedra and steel hedgehogs on the beaches, others at COHQ were undertaking trials to find the most rapid way of dealing with obstacles, and the probable damage they would cause at different states of the tides. At the end of April, Bernal was plotting the positions of known beach mines, and also working out their charges and fusing.75 The results of these endeavours were incorporated into the detailed orders for the landing.76
As the build-up to D-Day intensified, Bernal naturally became anxious about the quality of
the charts he had produced. He worried that his new maps were still not detailed enough and requested new hydrographic soundings.77 In particular, he was concerned that opposite Bernières landing craft would be in danger of grounding on the rocks. Once again the unlikely figure of Abbé Huc came to his aid. Huc’s geological interests extended to the distribution of glacial erratic rocks.78 He had explored the Bay of Calvados with local fishermen, whose intimate knowledge of the waters owed nothing to charts and who knew the rocks by individual names, such as Dos de L’Ane and La Vieille Femme. The abbot took cross-bearings on the rocks at low and high tides to plot a safe passage through them. The work of Abbé Huc was recapitulated by plotting the positions of the rocks from aerial photographs at known states of the tide so that safe passages could be identified.79
On 23rd May, Bernal travelled down to Southwick House, north of Portsmouth, where Eisenhower had established his operational headquarters. There he briefed Admiral Ramsay and Rear Admiral Vian, who was to command the naval task force that would transport the British 2nd Army, on the accuracy of his rock maps. He then had meetings with the navy hydrographer, and the following day they continued to work on beach maps using aerial reconnaissance photographs. Bernal was still studying ‘Huc’s monograph’.80 On 25th May, those holding naval orders for Operation Neptune were ordered to open them, and Bernal discussed the forthcoming assault with Blackett, who was at Southwick House in his capacity as head of Operational Research for the Admiralty. Sage attended a final meeting on underwater obstacles; his last map revision was completed on 31st May.
The timing of D-Day was predicated on the tides and, of course, the weather. The landing on the beaches was intended to take place at dawn on the half-tide with the tide rising. This was so that the landing craft would be grounded to seaward of the densest obstacles on the beach, and would float off easily after discharging their human and mechanical cargoes. If the craft landed at high tide, many would detonate mined underwater obstacles, and landing at low tide would expose the attacking troops for too long on open ground. Peter Danckwerts, who had started the war as the Bomb Disposal Officer for the Port of London, had been nominally sharing an office with Sage since the beginning of 1944, although Sage ‘had so many irons in the fire that he was seldom there’. Danckwerts recalled: ‘There was nearly a breach of security because of Bernal’s desire to be on the beaches by D+1. His lank locks had to be shorn and he had to be kitted-out with battle-dress and ammunition boots. All this took some time and he was not a particularly military figure at the end of it.’81
Bernal was driven back to Southwick House on 5th June, the day originally set for the invasion. The weather was poor and so the operation was put on hold. On reaching Portsmouth, Sage noticed empty parking strips that ‘had been so full of tanks and guns two days before’.82 He sought out Blackett, and the pair went for a walk through the maze of tents and huts surrounding the main building; they emerged on the Downs and ‘looked out on the sea where the whole Expedition lay just about to start… It was an immense assembly of ships but against the cloud and the sea, it looked very small.’83 Blackett thought it was silly of Sage to go, as did Sage to some extent. He knew that there was nothing he could do now to influence events, but felt that he had to be there and would never forgive himself if the operation went ahead and he missed the opportunity to observe what actually happened. He went to bed at midnight, after preparing ‘all my heads of enquiries’, knowing that the fleet had sailed. Waking at 4 am, he ‘carefully dressed in the very doubtful disguise of a naval officer’.84 The weather was bad and Sage was worried that this would diminish the effectiveness of the air bombardment on the far shore, but there was the compensating advantage of genuine surprise, suggested by early reports of German coastal batteries ‘firing very feebly’. After a three-course breakfast, Bernal listened to the early news trickling in; it did seem as though things were going better than predicted. Footholds had been gained on several beaches, although there were still no reports from the Americans.
On the afternoon of D-Day, Bernal sailed across the rough English Channel in a fast MTB.
The boat was alive. It swung from side to side and leaped up over the waves to come crashing down and sending up sheets of foam. It was no use trying to keep dry but it was so exhilarating that it did not matter. We began to pass the convoys of the second wave: hundreds of LCTs [Landing Crafts for Tanks] and all kinds of other craft wallowing along in the waves while we shot past. The wind rose as we got towards the centre of the Channel and the seas were high… Then the sky began to clear… [and] the whole journey became altogether a joyous one. The crew were all young, I suppose the oldest was twenty two; we were all excited but we could not talk except to point, between the roar of the engine and the crash of the waves. We began to pass returning convoys and to look for signs of action; a few were on tow, others showed holes made by mines – but their return at all meant success. This was not going to be a second Dieppe. How well I remembered those battered and scarred LCTs – the few that got home.
The sky was now all blue except that a pile of clouds lay on the southern horizon and clouds over France. Then I saw a very thin grey line. France that I had not seen for four years. Then the shapes began to appear. All around cruisers, battleships, merchant ships and LSTs [Landing Ships for Tanks] and hundreds of other ships. We could see the coast clearly now – the coast already burnt into my memory, having poured over so many maps and photographs. I knew every bit of it. The distant steeples of Langrune and Luc: the noble steeple of Bernières rising above its woods: the water tower above Courseulles: the hill of Mont Fleury and the lighthouse of Vire. The village of Rivière with the children’s sanatorium: and then, beyond it in the next dip – Arromanches. Arromanches where I had been ten years before, such a failure and sad turning point in my life. They were fighting still in Arromanches: you could see occasional little flashes. The lower part of the coast was covered with smoke from fires. The big ships were booming out – but a desultory bombardment. Shells seemed to be falling beyond Cap Montvieux: the sky clouded again and the sea stayed rough.
The MTB swung alongside a large naval ship – Sage managed to time his jump onto the rope ladder and scrambled aboard. Once inside, he realized how cold and wet he was, but he was soon standing at the bar downing ‘excellent and unobtainable’ drinks with some naval officers he had known at Cambridge, who were amused to see him in uniform. They sat down together in the wardroom for dinner, and Sage listened to the latest news on how the beaches had been secured by the British, but there was still no news at all from the Americans. At nine o’clock, they all listened to a speech on the radio by the King – ‘a strange, halting speech’ – followed by the playing of the national anthem with the officers standing to attention rather casually. Later the ship’s siren sounded and Sage came on deck to witness the ships firing flak at some distant planes, producing ‘beautiful streams of red fire: fountains rising and falling, swaying and twisting in the sky’. Then the bombs started to fall and he found to his surprise that his teeth were chattering. He was not ‘rationally scared but somehow the isolation of being in a ship was worse than any raid on land’.85 Lines from John Donne’s Elegy Love’s War came into his head.
To mew me in a ship, is to enthral
Me in a prison, that were like to fall.
He slept uneasily for a few hours lying on a bench in the Commodore’s cabin. Very early the next morning, he and the Commodore decided that they would try to go to the beaches. Just as Sage was gathering his things together, the ship shuddered and there was a loud crash.
We had been hit forward about thirty feet from where I was. In a few seconds flames were rising to the height of the mast. The wind was throwing them through the companionway and along back towards me. I worked it out: it was a bad conjunction. The ship lay head to the wind and the fire would be driven along and have most chance to spread. The sea was rough and the chance of getting out the boats, which were almost certainly too few, wou
ld not be great. I was probably the only man on board without a Mae West. I had procured an excellent one, but had left it behind at H.Q. I remembered studying the statistics of the bombing of ships, how one in three caught fire, and remembered the burnt out hulks in Tripoli harbour. But all this was not frightening, it was simply irrevocable fact. The fire parties started running up with the hose… the whole anchorage was alive with flak… everyone was on edge… any plane in sight [Spitfires included] would have been fired on. Then, in practically no time the flames began to die down a little. I moved forward. At the edge of the deck I could see the body of one of the A.A. gunners lying up against a rail, clearly dead, already pale and distorted and it was less than ten minutes since the bomb had fallen.86
Bernal and the Commander decided to try to go ashore but the heavy swell and strong onshore wind made it impossible to land. The weather on D-Day+ 1 was even worse than it had been on D-Day.
There was nothing for it but to turn back. Now we were moving in the teeth of the wind, very slowly and much beaten by the waves. We got depressed. In weather like this it would be practically impossible to land supplies or reinforcements for the assault troops. After two hours we got back to the dispatch boat. It was more difficult to get on board than ever: both vessels were pitching: there was nothing for it but to judge one’s time and jump. Both of us were feeling pretty sick, wet and cold but revived in a little time, enough for coffee and sausages.87
Before long, Sage was playing poker with a group of senior officers, who were all aware that the fate of the whole expedition depended on the weather. Bernal had talked to the two meteorological officers at Southwick House the night before D-Day, discussing how the accuracy of forecasts could be measured. He remembered how they had predicted a complicated series of depressions such as had not been seen in living memory. It was now noon Wednesday, when they had said there might be a slight improvement.