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Monday, January 3, 2011

Overlord Part III: The preparations.

"In preparing for battle, I have found that plans are useless, but planning is indispensable."  Dwight David Eisenhower


When, in 1942 America’s untested troops stormed ashore in Algeria and Morocco, FDR had appointed Dwight David Eisenhower to lead them.   After some heavy negotiations, Roosevelt secured his leadership for Operation Torch, the Allied invasion of North Africa.  The US would lead the invasion, despite no real battle experience against the Germans yet as of November of 1942, because the initial target would be French North Africa.  The French colonies in North Africa, after the Fall of France were defended not by German units, but by the Vichy French.  The Allies were hoping that, despite the legal fiction of neutrality -- French troops were actually functioning at the pleasure of the German victors -- the Vichy troops would not put up much of a fight.  There had already been serious friction between the British and Vichy when the British, concerned that the Germans might get control of some ships of the French fleet, attacked the French Navy in Vichy waters, so the British were probably not the best choice.  The French capitulated quickly after tense negotiations, and the success of the operation led to Eisenhower’s rise to commander of the Supreme Headquarters, Allied Expeditionary Forces (SHAEF) in December 1943.  His next major assignment was the planning of Operation Overlord.

Eisenhower was chosen because he was a diplomat as much as a warrior.  He had the responsibility of balancing the tough egos of the top British and American and Free French commanders who were competing with each other to show the largest contributions to the Allied war effort.  He also needed to manage the inter-service rivalries of all of those forces: strategic air forces, tactical air forces, naval and ground forces of each of those countries would need to be coordinated in such a massive and complex invasion.  There was ethnocentrism and competing agendas as well.   American foreign policy was explicitly anti-colonial, a severe sore point with their allies.   The Free French and the British were defending empires upon which the sun was just beginning to set.  Furthermore, the French were very eager to show they could liberate their own country, and fought the lead taken by the Americans or British despite the fact that America provided almost all of their transportation, equipment and supplies and many of their forces were staying in England.  So the plans that were worked out required a delicate balancing act from their commander.
Eisenhower planning for Overlord, flanked on his right (our left) by General Bernard Montgomery, commander of the British ground forces, and left by British Air Marshal Arthur Tedder, who helped Eisenhower battle British and American strategic air force commanders who did not want to subordinate their air offensives to the invasion plans!  This was Eisenhower's hardest fight of them all!
The invasion itself looked like a long odds gamble to the Eisenhower because of several factors.  The first limitation was that the invasion could succeed if it took place where the Allies could control the air.  Air attack on the landings needed to be prevented, which meant that the Atlantic coast of France was pretty much the only choice.  Southern Brittany was lightly defended but far from British ports and airfields, and far from the eventual objectives -- Berlin and the Ruhr industrial center.  Belgium and Holland were close to these, but too vulnerable to German air and naval concentrations to risk an assault.  French beaches had a large tidal surge, so only certain beaches were suitable, and timing had to be chosen with great care so that landing craft could sail over German obstacles and not disgorge the troops in water too deep for them, or too far out from the beaches.  Men in the water would be slowed down and too vulnerable to enemy fire.  If they landed in water over their heads, they would sink and drown with their heavy packs. Weather would limit operations.  It would be impossible to go if the seas were too rough or the skies too windy or foggy for the effective use of allied air or sea power.  A full moon was needed for airdropping the parachute divisions.  Germany had fortified the beaches with concrete pillboxes and artillery emplacements, mines, barbed wire and a host of obstacles.  And the Allies would only be able land a small percentage of their forces assembled in Britain in the first wave.  The Germans would have 58 divisions on or near the coast; the Allies would be able to land only eight.  The odds against success were pretty long -- unless the Germans could be prevented from quickly concentrating 58 against 8!  

Eisenhower's plan:  German Dispositions and Allied plans for the Battle of Normandy.  The crucial German panzer divisions are in dark red.  German units with an empty rectangles are fortress troops, those with an 'X' are regular infantry.  Pas de Calais is not marked, but is the area immediately east of Dover full of fortress troops, and targeted for an Allied diversion.  Those green areas in Germany were objectives of the British and American strategic bombing offensive that Ike needed to divert to destroy the French transportation system in preparation for the invasion.


Once the troops were ashore, they would require supplies.  Soldiers could only carry the food and ammunition they needed to fight a full effectiveness for two or three days, and much less than that if operations were going to be as intense and prolonged as could be expected.  The invading troops would be pitted against some of Germany’s best military units.  The Germans would have the use of the full French road and rail nets to supply their troops, and they had had years to create supply depots and fortifications to help support their troops.  The invading forces would have to carry everything on their backs initially.  For this reason, the Allies put a very high priority on quickly seizing a good deep water port and there were only a few really good ones along the entire French coast.  While the Allied troops weighed these factors in arriving at a plan, the Germans were also looking at them, trying to predict where their enemy would strike, and they were fully aware of the Allied supply challenges.  The best ports would be heavily defended.

Technological Innovations:

Nowhere is the story of Allied inventiveness more deeply validated than in the devising the technological solutions that made amphibious assault possible.  In all of World War II, as complicated and risky as these operations were, I know of only two failures.  The critical one was a raid on Dieppe on the coast of France in 1942.  This raid cost 3,000 Canadians their lives when they landed on well-defended beaches without the engineering capabilities to quickly overcome the German fortifications.  Despite the severe sacrifice, Dieppe taught the British many valuable lessons about conducting amphibious assaults.  To avoid this vulnerability, they invented machines that could protect them:  “Hobart’s funnies,” tanks that were designed to clear mines and barbed wire, tanks that were armed with flamethrowers, tanks with huge mortars for destroying enemy field fortifications, tanks that could swim ashore on their own power, and armored bulldozers that could help to carry on the work of assault engineers more safely under enemy fire, clearing obstacles on the beaches.  Assault engineers had the unenviable job of clearing all these defenses so that the infantry could get to the enemy.  The British also greatly expanded the role of naval gunfire support and redesigned their tactical air arm so that troops could get more support on the beaches in response to the weaknesses in these arms discovered at Dieppe.  All of these innovations would serve to make D-Day’s beach landing more successful than that at  Dieppe.  

Three examples of Hobart's Funnies in a contemporary museum.  On the left is a Sherman tank fitted out with a dual drive system so it could swim under its own power to the beach.  The middle vehicle is like a DUKW, or 'duck'.  It is a boat until it hits the beach, and then it acts as an armored cat.  The right-hand vehicle is designed to thrash the  ground with the chains on that roller so as to clear a path through minefields.
The Americans had already developed effective landing craft that could reliably bring troops ashore on beaches.  These were called Higgins’ boats, named for their inventor, Andrew Higgins of New Orleans, Louisiana.  (Higgins adapted designs for swamp boats used on the bayous where it was necessary to have very shallow draughts:  A boat that goes too deep into the water gets hung up on lots of obstacles in the swamp.  So, landing craft benefited from riding very high in the water. There is an entire museum devoted to this story in New Orleans that is worth visiting if this topic is of interest).  In 1944, landing craft were a critical bottleneck in the Allied war effort, as these tended to get expended in great numbers in every invasion.  While Operation Overlord was the top priority of the Allies in 1944, landing craft were needed everywhere, including for an invasion of the French Mediterranean coast planned for early August of 1944, and in the Pacific, where they were the mainstay of every US island assault.

Troops disembark from a Higgins boat.  By the time of the Overlord invasion, the Allies had specialty craft for landing tanks, vehicles and supplies, but Higgin's boats were the mainstays of infantry landings.

The Allies had almost three million troops allocated for deployment to the invasion of France, but would only be able to land 160,000 in the initial assault.  After that they would have to build up their forces as quickly as possible. Despite generally adequate shipping, this would prove a very challenging task.  Troops not only needed to be transported, but supplied with every item needed to sustain offensive operations.  Supplies had to be stockpiled in Britain and then loaded and shipped to France, and then would need to be unpacked and distributed to the troops.  Allied innovations include “Mulberries” the code name for a plan to transform the landing beaches into serviceable port facilities; and PLUTO, an underwater pipeline for pumping fuel from Britain to Normandy.  These would begin deployment the moment the landing beaches were secured.

One of the Mulberry pier-heads before it was sunk in position on the beach.  Mulberry components all had to be floated across the English Channel, and then sunk at the Arromanches or Omaha Beach landing sites.
A rare aerial photo of the Omaha Beach Mulberry.  This photo was taken June 12, 1944, just 6 days after troops hit the beach, and a week before the facility was destroyed in a storm.  The Arromanches Mulberry survived the Normandy Campaign, but much of it was later cannibalized when better ports were captured and made operational.

German Defenses:

The Germans had left a sizable occupation force in France after their victory in 1940, and after the Dieppe Raid, they expanded it.  Hitler and Goebbels would brag in radio addresses of the invulnerability of Festung Europa (Fortress Europe), and Germany did devote considerable resources to protecting the French Coast.  On the other hand, in the light of a possible Allied invasion, ensuring the security of French borders was a significant challenge.   In an inspection in 1943 Erwin Rommel realized that although the French ports were well fortified, the beaches were not.  Rommel himself was put in charge of upgrading the defenses.  He found everything he needed -- from troops to concrete, guns, land mines and barbed wire -- were in shorter supply than his requirements due to the immense demands of support for the Eastern Front.  While Rommel’s fifty-eight divisions would greatly outnumber any initial Allied force that could assault the beaches, Rommel didn’t know where they would attack.  He had to defend a 500-mile-long coast because the Allies could land almost anywhere, given their control of the sea and the skies.  Rommel also had to deal with the variability of the quality of the available troops.  These divisions ranged from full strength panzer divisions -- units armed with Germany’s best tanks and crack troops, to fortress garrisons comprised of partially disabled war veterans, under-aged and over-aged soldiers, and ‘Ost’ battalions of captured Poles and Russians who preferred military service to being worked to death in the concentration camps of Eastern Europe.  Many of these troops might not fight effectively in battle.

Field Marshal Erwin Rommel inspecting Festung Europa.  In 1943, it was mostly Nazi propaganda.
Rommel also faced the difficult choice of whether to put his best units -- the armored divisions -- on the beaches or hold them in reserve.  He knew that if he could arrange to meet an Allied attack on the beaches with his heaviest firepower, his forces could crush the landings at the outset.  The problem was that, if he proved incorrect in his guess about where the landings would take place, those top units would be stationed on the wrong beaches and would take longer to move into position to attack those Allied soldiers who made it to shore.  In the end, the decision was taken from Rommel’s hands by Hitler and the High Command, who ordered that the armored formations would be kept in reserve.  Hitler reserved to himself the decision about when to release some of the panzer divisions.  Ironically, this meant that Eisenhower, who would be coordinating the forces of many different nations, would have a unified command and full authority to commit his forces.  Rommel, who commanded only German forces in France, would not have the authority to commit some of his best troops.

Battery Lindeman, which shelled Dover from near Calais.  These made great propaganda photos for the home front, but Rommel had too few massive forts like these, and too much coastline to cover. 
Which Beaches?

The Allies believed that two best locations for the Allied assault on France were the Pas de Calais and Normandy.  The ‘better’ of these, Pas de Calais -- immediately across the Straits of Dover from England -- had many advantages.  It was the most direct route to Germany, closer to the campaign objectives.  It was also at the narrowest point in the English Channel, making the shortest possible trip from English ports to France, and it would be easier to defend from any possible interference by German submarines or patrol craft in the narrower waters.  It was already east of several formidable defensive barriers the Germans could use in their defenses, including the Seine Valley we are sailing now.    The area also held the promise of opening up a number of excellent ports, including Dieppe, Dunkirk and Calais itself, although the Allies did have reliable intelligence suggesting that these were heavily defended.

The other good choice was Normandy.  It was less heavily defended, was relatively easy to cover by air, was close to the major port of Cherbourg,  which might be quickily taken, thereby helping the Allies supply their troops.  Normandy was farther away from the German border, and that might mean that if the Allies could get reinforcements quickly to Normandy, perhaps they could defeat a portion of the German army there before all of the Germans mobile forces could be concentrated.  In their final analysis, invading Normandy seemed to the Allies the best way to prevent 58 from being brought to bear on 8.

The Key Solutions I:  Strategic Air Interdiction

The Allies launched two successful campaigns prior to the invasion that greatly aided in overcoming the German’s initial numerical advantage.  The first was a strategic bombing campaign that targeted bridges, ferries and river transport, railways, railroad marshaling yards, and all manner of transportation resources.  The purpose of this was to inhibit the German’s ability to quickly concentrate their forces in France.  Moving armored divisions by actually driving tanks down the road was slow, inefficient, caused lots of wear on the tanks, and was very hard on the roads.  So anything that made them more difficult to load and transport would mean that the tank divisions would arrive with more broken tanks before the battle on the ground even started and expose them to Allied air attacks as they came to the battle.  This bombing campaign resulted in the destruction of hundreds of bridges, and today you can see the beautiful brand new ones France needed to build after World War II to replace those destroyed in this campaign.  But the bombings also resulted in ‘collateral’ French casualties and damage to other buildings and  to cultural sites.  We saw evidence of this bombing campaign that still remains over 50 years afterward.  But the bombing did have another significant impact: it cleared the skies of Luftwaffe defensive forces.  When the invasion came, enemy fighters and bombers would scarcely make an appearance, because German losses had dictated the withdrawal of such forces for the defense of Germany itself.

 The pre-invasion bombing from the German point of view!

The Key Solutions II:  Psychological Operations:

The second was a campaign of disinformation meant to ‘sell’ the Germans on the idea that the Allies would invade the Pas de Calais.  The intelligence campaign used deception and misdirection including:  planting false papers on the corpse of an Allied officer which implied a Pas de Calais invasion site, then arranging for his body to wash up on the coast of France; withholding General George Patton -- America’s best tank commander, who Germans may well think would be central in any invasion – from the Overlord operation and assigning him to a phantom army poised to invade Pas de Calais.  Fake units, complete with fake barracks and vehicles and phony communications signals were assigned to Patton’s ‘command.’  British intelligence had cracked Germany’s Enigma code system, and German communications using this decryption device were monitored for signs that the Germans were taking the bait.  The Allied bombers left several radar sites in Pas de Calais untouched immediately before the invasion, and on the date of the genuine landings, a fleet of ships was sent to be picked up by this radar to keep the deception convincing right up to the moment the troops were assaulting the Normandy beaches. 

An Enigma machine used to encode secret German radio transmissions.  The capture and decoding of one of these was the Allies' most closely guarded intelligence success of World War II.  In the Normandy Campaign it was mainly used to see if the Germans remained convinced of a Pas de Calais invasion.
This disinformation campaign was very successful, and managed to convince many in the German High Command, including Hitler, that Pas de Calais was the indeed the target.  And that conclusion was probably confirmed for Hitler when his astrologer read the same prediction in the stars!   Hitler was slow to allow the movement of troops from Pas de Calais, for that reason, and the Germans thought for several weeks after the troops had landed that the Normandy invasion was only a diversionary attack.  They were, in fact, so convinced of this that when the invasion occurred, the Pas de Calais ports were so heavily defended that some of them held out until the very end of the war, and important German mobile formations were withheld from the Normandy battle altogether.

The Allied Assault Plan:

The plan called for a beach landing of the assault elements of 5 infantry divisions, two American, two British, and one Canadian.  The three Commonwealth divisions would each be reinforced by a tank brigade, including those fancy vehicles meant to help clear the beach defenses.  The largest air drop yet planned in the war -- two American parachute divisions and one British -- would land on the flanks of the beach to disrupt any efforts the Germans might make to reinforce their defenses on the beaches themselves.  In the critical first hours of the invasion, the Allies could project only 160,000 men against an unknown number of potential defenders.  Everything would depend on getting ashore quickly and then off the beaches to push the defenders back so that the Germans could not shell the landing sites with artillery as reinforcement and supplies were brought in.  

The final Allied plan.  Note that Cherbourg, the good port, is at the end of a peninsula and the US 4th Infantry Division does not need to advance very far to the west to isolate it!  The city of Caen on the east would be easy to defend from German counterattacks, if the British and Canadians can seize it quickly.


Of all the variables that Eisenhower could plan for but could not control, the weather was the critical wild card.  There were only brief windows each month in which the moon was full so that airborne forces could see to be dropped properly, and the tide was high enough to clear the German obstacles on the beaches so that the landing craft could get close enough to give the assaulting soldiers the best chances of success.  The first window in May of 1944 came and went:  the Allies were not ready and the weather was too unpredictable to take the risk.  The next chance would come June 5-7, and another would follow June 19-20.  The sooner the Allies could go, the more time they would have in the best campaigning conditions before rain and snow slowed operations in the autumn and winter.  But rain and high winds or choppy seas during these invasion opportunities would make the landings too risky.  The longer the Allies waited, the more opportunity the Germans had to bolster their defenses, and the greater the risk that Allied security would fail and the Germans might correctly assess the landing location.  Allied intelligence thought the Germans were unaware that Normandy was the chosen site, but they couldn’t know for sure whether the Germans appeared to be focusing on Pas de Calais because they were buying the false clues – or because they were engaged in their own disinformation campaign.  If the Germans put their primary strength in the sites where the Allies planned their landings, the Allied invasion was doomed.

The Sum of All Fears:

With all preparations made, the best guess of the Allied High Command was that the assaulting units would take 20% casualties, but 40% was not beyond the realm of real possibility.  In other words, the invasion was expected to cost the Allies as much as 60,000 dead and wounded on the first day.  Furthermore, Allied leaders knew that losses that high could cripple the ability of the remaining troops to function effectively.  They were perfectly aware that most military units ceased to be effective fighting forces when casualties reached that level.  They were betting that the impossibility of retreat would mean that these units would keep fighting, but that assumption was unproven.  

The fate of the three divisions being parachuted on the flanks of the beach was also a concern.   Parachute divisions were elite, highly trained troops but might have to bear the brunt of the counterattacks by veteran German armored units and would not have heavy weaponry to fight them off for very long.   They could only be lightly armed and there was no way to get the tanks, heavy artillery or anti-tank weapons they might need to them by airdrop.   This too was a gamble; there could be no guarantees beyond what solid preparation might provide.  It is easy to appreciate the crushing sense of responsibility Eisenhower felt having to make the command decision to launch the invasion with these expectations.  The deaths of up to 60,000 men gambled against the possibility that the Germans would realize that Normandy was the target site and fortify and garrison it in time to crush the invasion. When the time came to make the call, he would be able to poll the commanders immediately beneath him, but the ultimate authority was his.
Eisenhower reviewing American paratroops immediately before Operation Overlord.