Is There Any Reasoning As To Why D-Day Normandy Landings Were Specifically Planned For May/June?

[Redwolf915]

D-Day happened on June 6th 1944. It was delayed due to bad weather and tides. They wanted a spring tide so the invasion had to happen near a full Moon.

But what about Fall, Winter and Spring? Would any other month have been suitable or less suitable for the English Channel invasion? I imagine November through March might have waters that are very cold and would be a hindrance for invading troops. On the other hand I don't know anything about this water, so that's what I'm curious about!

 

[Director]

Weather had to be pretty calm since a lot of the smaller landing craft had to cross the Channel. Phase of the moon and tides had to be right also.

Two of the technological tricks that made success possible were the portable breakwaters and the pipeline carrying oil products from Britain. None of that could have been done in bad weather - it was a (predicted) break in the storms that led Eisenhower to issue the Go order.

 

[Redwolf915]

Weather had to be pretty calm since a lot of the smaller landing craft had to cross the Channel. Phase of the moon and tides had to be right also.

Two of the technological tricks that made success possible were the portable breakwaters and the pipeline carrying oil products from Britain. None of that could have been done in bad weather - it was a (predicted) break in the storms that led Eisenhower to issue the Go order.

Could a landing be made in Winter months or is the water too cold for troops to get wet? Germany invaded Norway in April.

 

[Rubidium]

Remember, the goal was not just to get troops ashore, but to advance as far as possible (ideally defeating Germany by the end of the year, although obviously they fell short of that goal).

So you need to worry about not just the weather at the time and on the beaches, but also the weather for the months afterwards and in the interior. The French/German winter isn't as bad as the Russian winter, but it's no picnic to campaign in either, so you want plenty of campaigning time before that happens. The earlier in the year, the more campaign time you have.

There's also the issue that Stalin had been lobbying for the Anglo-Americans to open a second front for years, and the western decision-makers were worried that he might seek a separate peace if they appeared to be delaying. So delaying it to the winter of 1944 was a non-starter; June was already a delay from earlier planning for May.

 

[VTs]

Remember reading something (maybe Churchill's history..) about it being originally planned for May, but postponed to June because they needed the extra month of production of landing craft.

It was planned for 5 June, but the weather made it impossible for the airborne landings to go forward.

 

[Director]

Germany invaded an unprepared and almost undefended Norway by seizing the docks - that's how Blucher was lost. The Allies wanted to seize a port - that's what the delay was about; after landing on the beaches they had to bring in more men, equipment and supplies over the beaches to support a push west toward Cherbourg. Later, the Allies would struggle to take Antwerp and clear its docks.

So there was an absolute requirement for calm weather, a high tide to cover the demolitions teams taking out the underwater obstacles, clear skies for the paratroops, and so on and so forth. Plus there was the continual and vociferous British struggle to use those troops in the Balkans, in Norway or anywhere but in France. The landing date had been postponed again and again, and finally went ahead when the Americans decided that, if Britain would not agree, the Americans would shifty priority to the Pacific.

Landing craft inventory was a continual bottleneck - along with merchant shipping, it determined the rate of advance in the Pacific, stalled and almost ended the landings in the south of France, postponed D-Day and seriously crimped every offensive move. Providing landing craft for Anzio was really only possible by taking them from Overlord, and when Anzio stalled and it seemed the troops would have to be evacuated by sea, those landing craft were basically stuck in Italy.

At least, that's what I remember...

 

[VTs]

Germany invaded an unprepared and almost undefended Norway by seizing the docks - that's how Blucher was lost. The Allies wanted to seize a port - that's what the delay was about; after landing on the beaches they had to bring in more men, equipment and supplies over the beaches to support a push west toward Cherbourg. Later, the Allies would struggle to take Antwerp and clear its docks.

So there was an absolute requirement for calm weather, a high tide to cover the demolitions teams taking out the underwater obstacles, clear skies for the paratroops, and so on and so forth. Plus there was the continual and vociferous British struggle to use those troops in the Balkans, in Norway or anywhere but in France. The landing date had been postponed again and again, and finally went ahead when the Americans decided that, if Britain would not agree, the Americans would shifty priority to the Pacific.

Landing craft inventory was a continual bottleneck - along with merchant shipping, it determined the rate of advance in the Pacific, stalled and almost ended the landings in the south of France, postponed D-Day and seriously crimped every offensive move. Providing landing craft for Anzio was really only possible by taking them from Overlord, and when Anzio stalled and it seemed the troops would have to be evacuated by sea, those landing craft were basically stuck in Italy.

At least, that's what I remember...

Thanks for sparking some more brain cells in my head.

Some text :

The long debate between U.S. and British leaders over the strategy of the European war reached a climax and a turning point at the great mid-war conferences at Cairo and Tehran late in 1943. Since the decision to invade North Africa, a year and a half earlier, the debate had focused on the war in the Mediterranean, the British generally advocating a bold, opportunistic strategy, the Americans a more cautious one. On the surface, they had disagreed on specifics rather than fundamentals. Few on the American side advocated complete withdrawal from the Mediterranean, and U.S. leaders were as quick as the British to respond to the opportunity offered by the disintegration of Italian resistance in early summer of 1943. They opposed the British primarily on the choice of objectives, especially east of Italy. For their part, the British never questioned the principle that the main attack against Germany in the West, and the decisive one, must eventually be made from the northwest (OVERLORD) not the south. In the meantime, they argued, aggressive operations in the Mediterranean were not merely profitable but even essential in order to waste the enemy's strength and to contain and divert enemy forces that might otherwise concentrate on other fronts. But the debate was embittered by American suspicions that the British intended somehow to sidetrack, weaken, or indefinitely postpone the invasion from the northwest, subordinating it to peripheral and indecisive ventures in the Mediterranean that would serve their own long-range political ends. Since the British consistently disclaimed such intentions.....

and later...

The most spectacular achievement of American war production was in shipbuilding. American shipyards in this year poured out 19.2 million deadweight tons of merchant shipping, which was more than two and one-third times as much as had been built in 1942. Early in August, the Joint Chiefs of Staff informed the chairman of the War Production Board that they no longer expected merchant shipping to be the bottleneck of the overseas war effort. 2 Only one category of supply-landing craft-threatened seriously to limit Allied strategy in 1944. At Cairo and Tehran, indeed, the apparent necessity of choosing between a postponement of OVERLORD and abandonment of planned or proposed amphibious operations elsewhere was dictated by the shortage of landing craft-more particularly, of one type of landing vessel, the Landing Ship, Tank (LST). Less than 300 LST's were in existence in November 1943, almost all built in the United States. Of these, 139 were in the Mediterranean-67 of them allocated to the British under lend-lease-and, except for a small contingent, were all earmarked for transfer to the United Kingdom for OVERLORD as soon as the amphibious phases of the Italian campaign were completed. For OVERLORD, in addition, the United States had agreed the preceding spring to provide 62 more new LST's during the coming winter. The remaining new production of LST's was allocated to the war in the Pacific.

....

American military leaders and their staffs, on the eve of the Cairo-Tehran Conferences, were in a mood to force a showdown on the strategy of the European war. As they viewed it, Allied strategy since the decision to invade North Africa had been drifting steadily away from the north-western Europe orientation, agreed on in April 1942, and into a peripheral line of action that could only end in stalemate. Preparations for a cross-Channel invasion in spring of 1943 had been suspended, the British Isles almost denuded of American troops, and American resources had been diverted into the development of a new line of communications and a new invasion base in North Africa. The decision at Casablanca in January 1943 to attack Sicily had ensured that the Mediterranean would continue to be the main theater in Europe during 1943 and that no cross-Channel invasion could be attempted until 1944 at the earliest. Since then British persuasion and the ineluctable logic of momentum had drawn the Allies deeper into the Mediterranean-into Tunisia, Sicily, Italy, Sardinia, Corsica-and a long, uphill struggle still loomed ahead in Italy. Most alarming to the Americans was the persistent effort of the British to broaden the Mediterranean front eastward-by pressure on Turkey to enter the war, by proposals to seize ports on the Dalmatian coast and to step up aid to the Balkan guerrillas, and, most recently, by an ill-advised incursion into the Dodecanese Islands which had cost the British several thousand troops killed and captured and untold loss of prestige. Persistent dabbling by the British in this region raised, in American minds, the dread specter of military operations and political involvement in the Balkan peninsula, a land of inhospitable terrain, primitive communications, and turbulent peoples.

from CMH_PUB_70-7-1 Command decisions

 

[Redwolf915]

Remember, the goal was not just to get troops ashore, but to advance as far as possible (ideally defeating Germany by the end of the year, although obviously they fell short of that goal).

So you need to worry about not just the weather at the time and on the beaches, but also the weather for the months afterwards and in the interior. The French/German winter isn't as bad as the Russian winter, but it's no picnic to campaign in either, so you want plenty of campaigning time before that happens. The earlier in the year, the more campaign time you have.

There's also the issue that Stalin had been lobbying for the Anglo-Americans to open a second front for years, and the western decision-makers were worried that he might seek a separate peace if they appeared to be delaying. So delaying it to the winter of 1944 was a non-starter; June was already a delay from earlier planning for May.

THIS is the aspect I wasn't thinking of thank you!

I'm making a mod for Darkest Hour that creates coordinated D-Day and Sealion landings and I want D-Day to trigger before 1944 if the Allies are doing extremely well.

Sounds like ideally you'd want to start a campaign in Northern France in mid March when the frost is gone OR at least 6 to 8 weeks before the November freeze.

This may be why on 12 October 1940, Hitler issued a directive releasing forces for other fronts effectively canceling Sealion for the year. That and the lack of air superiority.

 

[Grandpa Maur]

Germany invaded an unprepared and almost undefended Norway by seizing the docks - that's how Blucher was lost. The Allies wanted to seize a port - that's what the delay was about; after landing on the beaches they had to bring in more men, equipment and supplies over the beaches to support a push west toward Cherbourg. Later, the Allies would struggle to take Antwerp and clear its docks.

So there was an absolute requirement for calm weather, a high tide to cover the demolitions teams taking out the underwater obstacles, clear skies for the paratroops, and so on and so forth. Plus there was the continual and vociferous British struggle to use those troops in the Balkans, in Norway or anywhere but in France. The landing date had been postponed again and again, and finally went ahead when the Americans decided that, if Britain would not agree, the Americans would shifty priority to the Pacific.

Landing craft inventory was a continual bottleneck - along with merchant shipping, it determined the rate of advance in the Pacific, stalled and almost ended the landings in the south of France, postponed D-Day and seriously crimped every offensive move. Providing landing craft for Anzio was really only possible by taking them from Overlord, and when Anzio stalled and it seemed the troops would have to be evacuated by sea, those landing craft were basically stuck in Italy.

At least, that's what I remember...

It was Antwerp sea route among Zeeland islands that needed clearing, the city and docks were captured intact immediately.

Anyway, this is right, the problem is that weather in autumn/winter in the channel is worse, and supplying troops on beaches would be problematic (in fact, one huge storm in middle of June was already bad, imagine it happening more often and the whole invasion is in jeopardy before Cherbourg is secured and repaired).

 

[Director]

One oft-overlooked aspect of the war was the tendency of commands to hold onto assets they were supposed - and required - to relinquish. This showed itself in the backlog of ships waiting to be unloaded, and in the hoarding of landing craft. The former made terrific floating warehouses and the latter were useful for all sorts of freighting, passenger transport and so forth. And then there were the 'funnies' - the landing craft converted into rocket launchers and all manner of other things.

The bottlenecks in Allied lift capacity were varied, but a lot of it was that the requirement projections were accurate and the foot-dragging in commands that had landing craft was substantial. And a lot of it was that the requirements for overlord kept going up - and the requirements for Pacific landings kept going up - and the British wanted Anzio - and so on and so forth.

Didn't help that they settled on landing ship-and-craft designs relatively late, or that production had to compete with everything else that was crisis=level-urgent like aircraft, submarines, escort carriers, merchant ships and so on ad infinitum.

 

[VTs]

Some more info

Roosevelt finally interposed to suggest a date for OVERLORD "certainly not later than 15 or 20 May, if possible." Stalin chimed agreement. Churchill promptly and emphatically dissented, and the atmosphere again became tense.

Ahh politics....

Before lunch the next day (30 November) Churchill decided to agree to a date sometime in May, and the British Chiefs of Staff came to the meeting with their American opposites that morning with specific proposals worked out on this basis!2 General Eisenhower would be allowed to keep the sixty-eight OVERLORD LST's in the Mediterranean until 15 January in order to ensure the early capture of Rome. This meant, by British calculations, that OVERLORD could not be earlier than June- but the British Chiefs were willing, in order to satisfy Stalin, to define this as "in May." They were also prepared to support an operation against southern France and, most important, to agree that no assault shipping earmarked for OVERLORD should be retained in the Mediterranean specifically for the Rhodes operation. The· key to this last concession lay in their final proposition: as a result of Stalin's momentous pledge -on the 28th to enter the war against Japan after Germany's defeat, they argued, the role of China in the coalition had been automatically reduced, and the whole case for an offensive in Burma in spring 1944, including BUCCANEER, had been weakened. The British now hoped, in short, to persuade the Americans to cancel BUCCANEER and send its assault shipping back to the Mediterranean, where it could be used to help mount the southern France operation

So originally "planned" for "May", but the US and UK knew it was first to be in the beginning of June.

 

[Director]

And the southern France landings were repeatedly canceled, reinstated, postponed and juggled - in part because the landing craft from Anzio were supposed to go to Britain but didn't.

Churchill seems to have been opposed to landings in southern France and insistent on making the effort in Greece or the Balkans even if Overlord had to be postponed again. Finally he took to calling it DRAGOON, saying he had been 'dragooned' into it.

The Americans were overly optimistic about landing in Europe in '42 or '43 - Eisenhower later said that the North Africa campaign was essential to shake down doctrine and train troops. But Britain was certainly opposed to landing in France and, had the strategic decisions been left to them, the war might not have ended for years... or ended with the Soviets owning everything to the Pyrenees.

In their defense, Britain was trying to maintain a world-class navy, air force and field army on a population far smaller than the US, Germany or the Soviet Union. Successful or not, the campaigns in France and Germany had to not be bloody.

 

[Rubidium]

Churchill basically believed himself to be a military genius, and further that the traditional and successful British way of war had been to launch peripheral attacks rather than attack the main enemy.

He'd regularly proposed it during WWI as well during his time as First Lord of the Admiralty (Gallipoli was his brainchild, but he also had a bunch of similar suggestions, including one proposal to invade Denmark by sea to force them into the war and open up a new front that way), and he continued it in WWII (the mentioned "Rhodes operation" is presumably the disastrous Dodecanese campaign, which was a pointless fiasco from beginning to end, and had also been something Churchill had been lobbying for for years).

Even the rest of the British high command thought he was nuts.

The important thing to understand about Churchill is that he was an arrogant madman who had the good fortune to be right about two of the most important foreign policy questions of his era (Hitler could not be appeased, and Stalin and the Soviets were not trustworthy post-war partners), which covers up his massive failures on almost every other question of note.

 

[Director]

@Rubidium - I agree, but with a slightly different emphasis.

The 'traditional' - by which we mean Napoleonic Wars - strategy was to use seapower, wealth and advanced financial methods to pay other powers to raise large armies and do the heavy lifting in Europe. If matters had remained as they were in 810-1812 (and political things never stay the same) then Britain would have been unable to field a large enough army to take France on directly.

What they did was send troops to support their long-time ally, Portugal. This turned into a major commitment by strategic creep, and as the vulnerability of French lines of communication was recognized. But France could have coped with Spain, had they not had to fight Russia, and then also Prussia, and then also Austria.

The strategy of 'blockade and poke at the fringes' is the strategy of a weaker power, just as commerce raiding is the strategy of a weaker power at sea. It can make the enemy bleed a bit, and delay a decision, but it cannot be decisive.

Germany in WW1 and 2 could not be defeated by such a strategy as rail transport made it feasible to speedily react to enemy raids unless they were in and out very quickly.

The main issue, as I see it, was manpower: after the catastrophes in France and Singapore (to name just two) Britain simply could not risk losing a large expeditionary force. The US had almost unlimited manpower and could afford to champion a bolder strategy which would decide the war more quickly.

 

[VTs]

You are correct, it is the Dodecanese Campaign. With possibility to open the Bosporus and Black Sea to transport material ro SU that way round. (anyone think these ideas have been thought sometime before... )

Churchill basically believed himself to be a military genius, and further that the traditional and successful British way of war had been to launch peripheral attacks rather than attack the main enemy.

He'd regularly proposed it during WWI as well during his time as First Lord of the Admiralty (Gallipoli was his brainchild, but he also had a bunch of similar suggestions, including one proposal to invade Denmark by sea to force them into the war and open up a new front that way), and he continued it in WWII (the mentioned "Rhodes operation" is presumably the disastrous Dodecanese campaign, which was a pointless fiasco from beginning to end, and had also been something Churchill had been lobbying for for years).

Even the rest of the British high command thought he was nuts.

The important thing to understand about Churchill is that he was an arrogant madman who had the good fortune to be right about two of the most important foreign policy questions of his era (Hitler could not be appeased, and Stalin and the Soviets were not trustworthy post-war partners), which covers up his massive failures on almost every other question of note.

Tradition for the UK was to maintain a balance (advantageous to them, of course) on the Continent, so no other European power would be able to challenge them, especially on the oceans.

This balance was achieved by allying with whichever nation need help to keep Britain's balance.

However, there was no one left to help do the balancing in 1940. And the UK was a seapower, not a land power. They could never hope to go it alone with a D-Day style invasion. So they had to have a hit and run, hit the weak spots, wear them down kind of strategy.

Churchill was just not adaptable enough after the entry of the US into the war and the course of the war to be willing to change his strategy.

@Rubidium - I agree, but with a slightly different emphasis.

The 'traditional' - by which we mean Napoleonic Wars - strategy was to use seapower, wealth and advanced financial methods to pay other powers to raise large armies and do the heavy lifting in Europe. If matters had remained as they were in 810-1812 (and political things never stay the same) then Britain would have been unable to field a large enough army to take France on directly.

What they did was send troops to support their long-time ally, Portugal. This turned into a major commitment by strategic creep, and as the vulnerability of French lines of communication was recognized. But France could have coped with Spain, had they not had to fight Russia, and then also Prussia, and then also Austria.

The strategy of 'blockade and poke at the fringes' is the strategy of a weaker power, just as commerce raiding is the strategy of a weaker power at sea. It can make the enemy bleed a bit, and delay a decision, but it cannot be decisive.

Germany in WW1 and 2 could not be defeated by such a strategy as rail transport made it feasible to speedily react to enemy raids unless they were in and out very quickly.

The main issue, as I see it, was manpower: after the catastrophes in France and Singapore (to name just two) Britain simply could not risk losing a large expeditionary force. The US had almost unlimited manpower and could afford to champion a bolder strategy which would decide the war more quickly.

 

[Avernite]

One additional reason for a May/June landing is probably daylight; May and June have some of the best daylight availability of the year, so on those crucial first days of fighting you have a short night (and as it happened, even that had a full moon) and a long campaigning day to put some space between the front and the beach.

And of course, a May landing also leaves the fairly good June and July daylight for follow-up campaigning, too.

 

[Grandpa Maur]

One additional reason for a May/June landing is probably daylight; May and June have some of the best daylight availability of the year, so on those crucial first days of fighting you have a short night (and as it happened, even that had a full moon) and a long campaigning day to put some space between the front and the beach.

And of course, a May landing also leaves the fairly good June and July daylight for follow-up campaigning, too.

Ah yes of course. There was a lot of arguments back and forth between tides and sunrise and whatnot. IIRC, the British had to attack at low tide or something like that despite the time of the day not beign right. Or something like that. I can't remember. But it was denfinitely a concern.

 

[Frank_Costello]

Ah yes of course. There was a lot of arguments back and forth between tides and sunrise and whatnot. IIRC, the British had to attack at low tide or something like that despite the time of the day not beign right. Or something like that. I can't remember. But it was denfinitely a concern.

The Invasion Force needed a low tide near sunrise, which occurs only during a full or new moon. This was a major concern during almost all Allied / American Amphib operations in both the Atlantic and Pacific.

Paras believed they needed a 'Late Rising Moon' that would illuminate the battlespace during the crucial parts of the jumps. That term, late rising moon, was made famous by Cornelius Ryan but was uttered by Bedel Smith.

June 6, the Moon reached its highest apogee at 1:19 AM over France with low tides at dawn to avoid the worst of the beach entanglements.

Eisenhower's choices were:

GO! Use the meteorologists projections and go now in imperfect weather conditions

or

wait two week for the New Moon to get low tides at dawn - hopefully

or

wait a full month to get the full moon / low tides at dawn - hopefully

An invasion around July 4th would be very patriotic to America but you just blew four weeks of combat operations in Summer weather IF Ike bailed on teh June 6 window.

The Germans, thinking the Americans would only invade in perfect weather, stood down while 'Hitler took a sleeping pill' while Rommel took his wife a pair of red shoes for her birthday.

In hindsight, it was almost perfect.

 

[Jopa79]

To answer the title - Is There Any Reasoning As To Why D-Day Normandy Landings Were Specifically Planned For May/June? - yes, there are at least two good reasons. The weather, of course, is one. Making the landings during early summer gives the Allies much better opportunity to have success, than let's say for instance, if the landings would have happened in November-February.

A second reason, not so well known, already earlier the Allied and the Soviets had agreed, Stalin would launch a simultaneous, a supportive offensive at the Eastern Front early summer of 1944, to draw the Axis' attention elsewhere from Normandy and by doing so, to give the Allies a better chance to make a successful landing. The Soviet Union launched a massive offensive against Finland at the Eastern Front, on June 9th, 1944, nearly resulting Finland to collapse at the end of the month.

 

[Darth Howard]

To answer the title - Is There Any Reasoning As To Why D-Day Normandy Landings Were Specifically Planned For May/June? - yes, there are at least two good reasons. The weather, of course, is one. Making the landings during early summer gives the Allies much better opportunity to have success, than let's say for instance, if the landings would have happened in November-February.

A second reason, not so well known, already earlier the Allied and the Soviets had agreed, Stalin would launch a simultaneous, a supportive offensive at the Eastern Front early summer of 1944, to draw the Axis' attention elsewhere from Normandy and by doing so, to give the Allies a better chance to make a successful landing. The Soviet Union launched a massive offensive against Finland at the Eastern Front, on June 9th, 1944, nearly resulting Finland to collapse at the end of the month.

Don't forget Bagration...