The invasion postponed

Early on the morning of 4 June 1944 General Dwight Eisenhower, Supreme Commander of the Allied Expeditionary Force, postponed the invasion of France by 24 hours. The Normandy landings, fixed in May for 5 June, were to take place a day later. The reason was the weather forecast: a depression was moving in over the English Channel, bringing strong winds, high seas and low cloud. The warships and landing craft were already loaded and some convoys were at sea – they had to be turned back.

War chronologies put it briefly: Operation Overlord was postponed by a day because of rough seas. That is accurate but incomplete. What decided the postponement was not so much the sea as the whole forecast for 5 June: the wind, the waves and, above all, the low cloud base, which would have prevented the air forces from bombing the fortifications, covering the landings or dropping the paratroopers in their designated zones.

The conference on the evening of 3 June

From the beginning of June the invasion commanders met twice a day at Southwick House near Portsmouth, the headquarters of Admiral Bertram Ramsay, the naval commander of the operation. Eisenhower lived in a caravan in a nearby wood. At these conferences the SHAEF meteorologist, RAF Group Captain James Stagg, presented a forecast agreed – with difficulty – between three teams: the British Meteorological Office, the Admiralty and the meteorologists of the US Army Air Forces. According to Stagg’s memoirs, the teams differed in their assessments, and the American team was markedly more optimistic than the British ones.

As late as the end of May the forecasts held out hope of a calm start to June. In the first days of June, however, the picture began to deteriorate and the meteorologists grew increasingly worried. On the evening of Saturday 3 June Stagg presented the commanders with the forecast for 5 June, which the American official history (Gordon A. Harrison, Cross-Channel Attack) summarises as follows: overcast and stormy weather, strong winds and a cloud base from 500 feet (about 150 metres) down to zero, and a situation so changeable that forecasts more than a day ahead were highly unreliable. The long spell of settled weather was coming to an end. After discussion it was decided to defer the decision for seven hours and meanwhile to let the ships sail from port as planned.

The haste was dictated by geography. The longest passage lay before Force U, which was sailing from the ports of Devon – among them Plymouth, Salcombe, Dartmouth and Brixham – towards Utah Beach on the east coast of the Cotentin peninsula. Its first convoys had put to sea on 3 June, as had part of Force O from Portland, bound for Omaha. Were the invasion to be postponed, these were the convoys that would have the furthest to turn back.

The forecast also drew on data from places far from Portsmouth. Among them were observations from the weather station at Blacksod Point on the west coast of Ireland. Although Ireland remained neutral, it passed weather data to the British central office at Dunstable. According to an account cited by the National WWII Museum in New Orleans, the observer Maureen Flavin reported rising wind and rain and falling pressure from there at 1 a.m. on 3 June – heralding the approaching depression.

The decision in the early hours of 4 June

The second conference met before dawn on Sunday 4 June – at 4.30 a.m. according to Harrison, a quarter of an hour earlier according to other accounts. Stagg had no good news. The sea was expected to be somewhat calmer than feared, but the cloud still ruled out air operations. General Bernard Law Montgomery, commanding the invasion’s ground forces, was ready to go ahead as planned. The air commanders were against: Eisenhower’s deputy, Air Chief Marshal Arthur Tedder, and the commander of the Allied air forces for the invasion, Air Chief Marshal Trafford Leigh-Mallory. Ramsay, as Montgomery noted, would not commit himself either way.

Eisenhower postponed the invasion by 24 hours. Harrison explains his reasoning: Overlord had only a very slender superiority on land, and only Allied command of the air made it a reasonable operation of war. If the air forces could not operate, the landing should not be risked. The agreed signal went out to the fleet, and the ships and convoys already at sea turned back to their ports and anchorages, to sail again a day later.

Not all of them did so at once. The Canadian official history (C. P. Stacey, The Victory Campaign) describes a Force U convoy designated U2A – 138 warships and landing craft – that failed to receive the signal. At nine in the morning it was 25 nautical miles south of the Isle of Wight and still heading for Normandy. Two destroyers and an aircraft were sent after it and managed to turn it round. Ramsay later wrote in his report that had this not been done, the convoy might have been detected by German radar, which would certainly have increased the enemy’s vigilance in the following days.

For the soldiers the postponement meant an extra day in crowded holds and on the decks of landing craft pitching in the rough sea. The small landing craft struggled back against the wind to sheltered harbours. Many men were seasick before they had even set out. The camps and ports had been sealed off for weeks, and the troops aboard ship already knew their destination – every further day of delay increased the risk of a leak.

The break in the weather

At 9.30 p.m. on 4 June the commanders met again in the library at Southwick House, with wind and rain raging outside. This time Stagg had unexpected news. The rain belt over the landing area would pass within two or three hours, and the clearance would last until the morning of Tuesday 6 June. The wind would ease and the cloud would permit heavy bombing on the night of Monday to Tuesday; the cloud base at H-Hour might be just high enough for observers to direct naval gunfire. Harrison sums it up as weather that was tolerable rather than ideal. For Thursday 8 June the meteorologists could not forecast anything at all.

Ramsay pointed out that half an hour remained for a decision. If the forces of the American Admiral Alan Kirk sailed for a Tuesday landing and were then recalled, they would not be able to sail again in time for Wednesday – the last day on which light and tides favoured a landing. Calling off the invasion therefore meant waiting for the next window, around 19 June: unloading the troops from the ships, risks to secrecy and morale, a moonless night for the paratroopers and a shorter season for fighting on the Continent. Eisenhower’s chief of staff, General Walter Bedell Smith, thought they had to try. Leigh-Mallory and Tedder still doubted whether the heavy bombers could operate effectively. Eisenhower asked Montgomery whether he saw any reason not to go on Tuesday. “I would say – Go!” Montgomery replied.

At 9.45 p.m. Eisenhower announced his decision. Harrison quotes his words: “I am quite positive we must give the order… I don’t like it, but there it is… I don’t see how we can possibly do anything else.” The orders went out at once. There remained a risk that the weather would deteriorate so badly that they would have to be cancelled, so one more conference was called. Accounts differ even about its time: Harrison writes of a meeting just after midnight, Stacey of a conference at about four in the morning of 5 June, while other authors, following the recollections of participants, give 4.15 a.m. The forecast had not changed, and the decision stood.

Eisenhower’s most often quoted words – “OK, let’s go” – were spoken at that point, early on the morning of 5 June, though here too versions differ: authors quote “OK, we’ll go”, “Well, we’ll go!” or “OK, let ’er rip”. Stacey remarks in a footnote that the accounts of witnesses and historians of those hours differ to a surprising degree. One thing is certain: the decision was Eisenhower’s alone, and the fleet set out for Normandy.

A note in case of defeat

Eisenhower knew that he was taking a risk that might end in disaster. On 5 June he wrote out in pencil a short communiqué to be issued if the landings failed. The text, held at the Eisenhower Presidential Library in Abilene, reads in essence: the landings in the Cherbourg–Le Havre area had failed to secure a satisfactory foothold and he had withdrawn the troops; his decision to attack at that time and place had been based on the best information available; the soldiers, airmen and sailors had done all that courage and devotion to duty could do. It ends: “If any blame or fault attaches to the attempt it is mine alone.”

Whether out of haste or fatigue, Eisenhower dated the slip “July 5” instead of 5 June. The note never had to be used. According to the memoirs of his naval aide, Commander Harry Butcher, Eisenhower came across it in his wallet on 11 July and handed it to him, remarking that he had written a similar note before every landing. On the evening of 5 June he also visited the paratroopers of the US 101st Airborne Division at Greenham Common airfield before they took off for Normandy.

On the other side of the Channel

The weather that forced the Allies to wait lulled the Germans into a false sense of security. German meteorologists had no stations to the west of the Channel, where the depressions came from, and the weather aircraft flying out over the Atlantic supplied data of limited value. Harrison stresses that they could not have foreseen the clearance that Stagg spotted. There is no evidence that the meteorologists explicitly assured the commanders that an invasion on 6 June was impossible, but the wind and the waves clearly dulled German vigilance. Kriegsmarine experts considered a landing possible only with calmer seas, lighter winds and better visibility – and on 5 June these conditions were not met. According to many studies, because of the weather German naval patrols did not put out into the Channel that night, and the naval commander in the West, Admiral Theodor Krancke, received the evening warnings without concern.

On the morning of 4 June, as most biographers have it, Field Marshal Erwin Rommel left the headquarters of Army Group B at La Roche-Guyon by car for his home in Herrlingen near Ulm. His wife Lucie’s birthday fell on 6 June, and he intended afterwards to see Adolf Hitler at the Obersalzberg and ask for the panzer divisions to be moved closer to the coast. He believed that with such weather and such tides the Allies would not strike in the coming days. In addition, a Seventh Army war game had been scheduled at Rennes for 6 June, and many divisional and lower commanders had been summoned to it – some of them left their headquarters before dawn. Over the previous few months Rommel had strengthened the Atlantic Wall, but at the moment of the landings he was not in France.

Its place in the war

The one-day postponement was the final act of the long preparations for the invasion, which had been completed in May with the briefing at St Paul’s School and the fixing of D-Day. On that same 4 June, while the fleet was returning to port, the Allies entered Rome – the first Axis capital taken in the war. On the night of 5/6 June Allied aircraft bombed the German coastal batteries, paratroopers landed behind the beaches, and on the morning of 6 June five infantry divisions came ashore in Normandy. The Germans, convinced that no invasion would come in such weather, were taken by surprise, and Rommel got back to his headquarters only on the evening of 6 June.

How sound Eisenhower’s decision had been became clear two weeks later. Had the invasion been put off to the next window, it would have fallen in the period 18–20 June – and on 19 June the Channel was struck by the most violent June storm in decades, which wrecked the American artificial harbour off Omaha. According to documents held by the Met Office’s National Meteorological Library and Archive, Eisenhower later wrote on Stagg’s forecast from those days: “I thank the Gods of war we went when we did.” Stagg described those days in his 1971 memoir Forecast for Overlord. The conference at Southwick House became one of the best-known examples of a decision taken under uncertainty – on the strength of a forecast that might have proved wrong, and in full awareness that responsibility for any defeat would fall on one man.