Source: Historical Section, COMNAVEU. "Administrative History of U.S. Naval Forces in Europe, 1940-1946." vol. 5. (London, 1946): 301-337 [This manuscript, identified as United States Naval Administrative History of World War II #147-E, is located in the Navy Department Library's Rare Book Room.]

CHAPTER IV
NEPTUNE OPERATIONS PLANS

PART I
THE ENEMY SITUATION

A. German Land Forces

  1. The defense of France and the Low Countries against Allied invasion was entrusted to the German "Commander in Chief West", Field Marshal von Rundstedt.1 The military force assigned to him to accomplish this task comprised Army Group D. Under C in C West (CinC Army Group D), the area to be defended was divided between four armies.

    1. The Fifteenth Army held the eastern channel coast from the Rhine to the Seine.

    2. The Seventh Army held the western channel coast and the Brittany Peninsula from the Seine to the Loire.

    3. The First Army held the Biscay Coast from the Loire to the Spanish frontier.

    4. The Nineteenth Army held the Mediterranean coast and the Italian frontier.2

  2. The German dispositions in the West provided for manning the various coastal sectors with static infantry, while the mobile divisions were held in reserve for counter attack purposes. Static divisions were assigned to the command of the appropriate army commanders. The mobile reserves, directly under command of Army Group D, were situated as close to the coast as possible, usually 20 to 100 miles inland and invariably at main communication centers. on the eve of the invasion (17 May 1944), Army Group D consisted of some 60 divisions, made up of seven operational Panzer divisions, three Panzer divisions in training, two Parachute

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    divisions, thirty-seven operational Infantry divisions, and ten Infantry divisions in training. Of these, forty-one divisions were static coastal defense troops, while about nineteen were mobile field divisions in reserve.

B. The German Defense Plan

  1. The German plan for defending Europe was devised so as to exploit two great advantages possessed by the defender of a sea front, namely: (1) the weakness and vulnerability of an assaulting force during the landing period, and (2) the slow rate of tactical build-up possible, with sea communications, as compared with that permitted by a well developed system of land communications. It was also designed to minimize dangers arising from German weakness in the air and on the sea.

  2. The enemy's policy for the defense of occupied coasts was, therefore, built upon two basic principles and one assumption.

    1. The assault would be met on the beaches and any penetration made was to be broken at the coast line. All defenses were placed as near to the coast as was physically or tactically possible, but were not in great depth, because of the length of the coast-line to be defended and the limited troops available.3 Supporting artillery was sited so as to cover the coast or seaward approaches to it. Beach defenses were continuously manned, and protected by concrete or armour. All headquarters and air and naval bases were well protected against air and air-borne attack;

    2. Static coastal defenses were to be seconded and supported by mobile reserves, so disposed as to permit quick reinforcement of any threatened coastal sectors, and in such numbers as to be able to build up for counter attack more rapidly than the invader could build up his forces from the sea.

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    1. The assumption was that an assaulting Allied force would be compelled to seek the immediate possession of a port, in order to discharge the vast quantities of men and material needed to fight the land campaign. Therefore, the invader was to be denied access to all ports. Defenses tended to be much denser and heavier near ports, estuaries and coastal regions giving access to ports. The ports themselves were locally defended by a perimeter system, especially directed against sea approach.

  1. In conformity with this general policy, no second line of defenses existed. The troops manning the coast and their supporting mobile reserves, were to remain in their positions until the bitter end. No prepared defense systems had been constructed in the interior of France or the Low Countries, as labor was not available for such work, even if the positions to be defended could be determined before the battle developed. Available resources and material had, therefore, been expended on strengthening the one really good defense line -- the coast. The existing French, Belgian, and Dutch interior defense lines, which faced the wrong way for German purposes, had been dismantled. Very little work had been spent even on the Siegfried Line, the West Wall of Germany itself. Inside the coastal periphery, prepared defensive positions were limited to the local defense of important objectives, such as air bases, major towns and a few strongly fortified Headquarters. Bridges and railway marshaling yards had been prepared for demolition on an extensive scale.

  2. In short the defense system was that of a continuous hard, thin "skin" often immensely strong, near vital ports for example, and always easily reinforcible from nearby concentrations of mobile reserves, but never more than "skin-deep". This skin was a blend of infantry fortifications, emplaced supporting artillery, and obstacles. once this skin was broken, no prepared positions remained, and the German armies would be compelled to meet the Allies in the field.

C. Coastal Defenses, Fortifications and Obstacles

  1. The fortifications consisted of a series of strong points, linked where necessary and practicable by continuous obstacles in the form of mines, wire, anti-tank walls, etc. In villages and towns on the seafront, almost any house might have its ground floor bricked in or reinforced with concrete to form a pill-box. Sea walls were made into strong obstacles. Anti-tank walls were stretched across the entrances to side streets. Major strong points were formed from suitable buildings at strategic places. Mines and wire were liberally used to reinforce these measures.

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    The coast itself had strong points at intervals of one to two thousand yards. Between these strong points was wire and rows of mines. All these defenses were sited as near the high water mark as possible, but some headquarters strong points were "staggered" in the rear. The average depth of the whole defense system, up to the battalion headquarters, was about two miles. In the vicinity of cliffs, strong points were sited at all possible landing places, and in all clefts or gullies that could give access to the land. Marshy land behind beaches was flooded. Roads and bridges were mined.

  1. Supporting artillery, composed of guns of all calibres and situated in a continuous coastal belt, covered and reinforced the infantry fortifications. heavy and medium coastal batteries, with intersecting arcs of fire, were capable of bombarding an attacking force as far, in certain places, as 20 miles from the shore. As the invader approached nearer he came within range of lighter batteries, field artillery, and howitzers. The beaches themselves were generally covered by enfilading fire, or by direct fire from mobile batteries inland. Artillery was directed by radar as well as by visual observations.

  2. In order to ham-string the Allied build-up by denying them the use of ports, the German coastal defenses were particularly dense and strong in and around all harbours and estuaries, even very minor ones. Density of defenses varied, not only near pots, estuaries and other vital points where they tended to increase, but also over the area as a whole. Variations in density reflected the distance from Allied fighter bases, the approachability of the coast, the strategic prospects of the hinterland, and so on. In areas where defenses were thickest they also tended to be intrinsically stronger, with guns of heavier calibre, pill-boxes of stouter construction, and strong points at closer intervals. In "weak" areas, the quality and morale of the troops, and their degree of alertness, was likewise inferior to those in "strong" areas.

  3. The Germans had constructed an extremely well equipped system of radar, along the north coast of Europe from Brittany to the Baltic. They placed great reliance on its accuracy and its dependability. This system was particularly complete between Den Holder and St. Nazaire, with a mixture of short range and long range sets, surface sweeping and air warning sets, and gun control equipment. In addition, there were three or four chains of GCI stations located behind the coast but in front of the German frontier.

  4. At frequent intervals along the coast, often associated with strong points, but always protected by surrounding wire,

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    the enemy had installed searchlights, sited to sweep to seaward and sometimes to cover the beaches. In and near ports these occurred with greater frequency.

  1. The defense system on the beaches consisted of a series of strong points, linked by obstructions, which were spaced at intervals, varying from one to three or four thousand yards. In the NEPTUNE area the average separation was about two thousand yards. These defense positions were generally thickest and strongest in positions facing Allied bases. They were rarely placed more than two miles behind the coast, and varied greatly in form and strength; from specially constructed series of concrete buildings (gun casemates, pill-boxes, magazines, control posts, personnel shelters) to single pill-boxes or weapon pits, with M.G. positions in open trenches. The wire and mines surrounding the strong points again varied in density and strength with the particular terrain and area. Such strong points were designed to afford each other mutual support by the fire of the light guns, anti-tank guns, and machine guns with which they were armed. They were in communications with each other and with regimental H.Q., itself housed in a major strong point. In the weak areas, the great majority of strong points were infantry positions only, while in strong areas almost half of the strong points were based on an artillery battery, a flack battery, a radar or communication installation, or some other important point. Nearly 40% of the strong points were manned and operated by naval or air force personnel.

  2. The following are some of the principles which the Germans followed, in laying out and siting coastal defense positions:

    1. The German policy was to provide, underground if possible, heavy shelters for their men with light weapons as well as in coastal batteries, from which they were to emerge to their guns after any bombardment, via trenches or covered passages. These shelters, with firing slits covering their entrances, were equipped for the maintenance of their occupants for considerable periods, even if isolated. Concrete 6 ft. 6 in. thick was used liberally and universally in heavily defended areas. Even in lightly defended areas it was some 3 ft. 3 in. in thickness.

    2. Fortifications, including artillery (except for howitzers) were sited well forward and, when possible, located along a line at the back of the beaches.

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    1. Defense positions were sited so as to cover beaches, inshore waters and sea approaches with enfilading fire.

    2. They were sited on low ground, whenever possible, in order to give the maximum danger zone.

    3. All defense positions were self--supporting (being provided with all-round fields of fire), and self-contained (being provided with independent stocks of food, water and ammunition). Battery positions, headquarters, radar stations, signals installations and other important positions, were protected by numerous garrison troops and by strong concrete fortifications. These were put underground, whenever possible, to provide greater protection against naval and air bombardment and against airborne attack.

    4. In order to economize manpower, maximum use was made of automatic weapons.

    5. Maximum use was made of obstacles against Allied armour.

    6. In coastal towns, civilian buildings were evacuated and reconditioned as fire positions, or demolished so as to clear fields of fire.

  1. A feature of the German coastal defenses was the extensive use of obstacles. They were designed so as to impede movement up to and off of the beaches and to protect defensive positions against assault from any direction.

    1. Mines were first in the category of "obstacles". They were laid in rows at the back of the beaches, sometimes almost at high water mark, sometimes up to a few hundred yards inland. They were disposed in staggered belts and were often surrounded by trip-wire, which served to give warning of intrusion to the local defenders. Mines were sometimes behind and sometimes in front of the barbed wire defenses. Anti-personnel mine fields were liberally used around strong points, while tactical anti-tank, anti-personnel and mixed mine fields were set between them. The normal density was one per yard, with a normal pattern of one to three belts each of three to eight rows, and with a normal depth of a field of from 50 to 300 yards.

    2. Barbed wire was used extensively, both on and off the beaches, between, and in front of, strong points. A line of underwater barbed wire was occasionally strung along the beaches as an obstacle to troops wading ashore.

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    1. Walls were very common obstacles. They were employed either as road blocks, or as a continuous breast work along beaches, promenades and roads. They were usually 61/2 to 10- ft. high, and 3 to 8 ft. thick.

    2. Anti-tank obstacles were sited wherever the natural geography of the coast provided a possible exit for tanks and motor vehicles. Steel obstacles of various types were widely employed, the most common types being the gate and the curved rail from the old French, German and Belgian defense lines, and the tetrahedron. Sea walls were reinforced and wired to turn them into more formidable obstacles. On the seafront and in built u places, the entrances to the side streets leading inland were similarly blocked. Ditches, which were particularly common, especially in low lying areas, were 40 to 60 ft. wide and filled with water. Dry ditches were occasionally employed, sometimes covered over, of a width of 9 t 15 ft. and depth of 8 to 12 ft. These obstacles continued further inland even though the defenses were a "skin" and confined to the coast, in order to deal with the possibility of errant tanks surviving the initial landing.

    3. Inundations were a popular German device. Extensive preparations for inundating wide stretches of low lying or marshy ground had been made, while some areas had in fact been flooded before the landings occurred.

    4. Under water obstacles had been installed along nearly all possible landings beaches, and sometimes even in front of cliffs and rocks, with the object of impeding Allied landings by breaking up or blowing up small boats as they beached or retreated.4

  1. Most of the beach obstacles in Normandy and Brittany were the ordinary steel anti-tank obstacles used on land. From the mouth of the River Somme northward, timber stakes

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    were ordinarily used instead of steel obstacles. The types of obstacles used were Element C, steel tetrahedra, steel hedgehogs, vertical steel rails, and timber posts. The spacing between units in each row carried from 8 feet to 50 feet, the tendency being to thicken them up as work progressed. Normally, there were three to four rows of steel obstacles located some 12 to 17 feet below high water mark, but sometimes these obstacles extended irregularly almost down to the low water mark. Waterproofed land mines of various types were attached on or near the obstacles.5 Sea mines were usually not laid close inshore to defend the beaches. Minefields were normally seaward of the coastal swept channels. In the immediate approaches to some major and minor ports, however, extensive inshore minefields had been laid.

  1. The defense of ports and estuaries was more developed and more concentrated than that of intervening stretches of coast. The enemy assumed that an invading force would be compelled immediately to secure adequate ports through which to pour the vast quantities of material needed by a modern army. His defenses were based on that assumption. Heavy artillery was sited so as to defend the approaches to all major ports. Every possible entrance was guarded by batteries of all calibres. Booms of various types, sometimes with explosive charges, were universal, and a few controlled minefields had been laid. Flame-throwers were available in a number of port areas. Piers and jetties were mined and sometimes had gaps in them. Pill-boxes were mounted on them, or in them. Torpedo tubes were installed in some harbors. Port defenses faced inland as well as seaward to guard against the possibility of a surprise attack from the landward side, and also to make it possible to hold a port, as a self-contained position, for as long as possible, even after it had been surrounded. Strong points and artillery were placed in a perimeter about the town. The "skin" thus became "port-deep".

  2. Ports were liberally stocked with water, food and ammunition, and were provided with self-sufficient army formations, equipped to withstand a considerable siege even after having been cut off. One feature of all port defenses was

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    the preparations made for demolitions. These were not defenses in the ordinary sense, but they constituted a part of the enemy's plan to deny the Allies the use of these ports. They were universal and complete. Quays were mined; block-ships (or barges for use as block-ships) were ready; locks, cranes and harbor facilities of all sorts were prepared for demolition. Ports were also heavily mined both ashore and in the harbor. Heavy anti-aircraft batteries on the coast were confined almost exclusively to the neighborhood of the ports. Mobile anti-aircraft units, principally for the defense of coastal airfields, were deployed as required.

  1. Estuaries which led to a port, or which might have served the purpose of a harbor or port, were similarly defended. Howitzers, fitted by their plunging fire for the task, were sited so as to drop a barrage across the estuary, while heavier batteries covered the seaward approaches. The mouth of the estuary often had a net or boom, and its shores were protected as if they were beaches. The smaller ports, and even minor havens, were similarly defended though to a lesser degree. The smallest harbor had a wire "boom" across its entrance. The quays were often mined, and pill-boxes and strong points were sited to deny entrance.

D. German Coastal Batteries

  1. German coastal batteries consisted of guns of every calibre, from super-heavy 16" guns down to old French 75's of the First World War, and varying in range and accuracy from very good to very bad. (The approximate location and types of the German batteries in the Normandy area is show in the accompanying sketch.) The following were the types and ranges of guns.

    1. Heavy coastal batteries (8" and over) had, as a rule, a maximum effective range of 40,000 yards.6

    2. Medium coastal batters (between 4.5" and 8") had a maximum range of 27,000 yards. The 155 mm. was the most common gun of this type.

    3. Light coastal batteries (between 3" and 4.5") had ranges up to about 20,000 yards. This category included old British and French guns, modern pieces and dual purpose anti-aircraft guns.

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    1. Howitzers, which were usually sited inland for planting fire on beaches or sea approaches, had ranges varying from 7,000 to 18,000 or 19,000 yards.

    2. A wide variety of ancient and modern mobile guns were situated in the NEPTUNE Area, usually in or near ports. Their maximum range classification in general followed that of fixed batteries of equivalent calibres.

  1. The Germans made it a general rule to site all classes of coastal batteries as far forward as possible, so that most of them stood very near to the beaches. Howitzers formed an exception to this practice and often stood several miles inland and on reverse slopes. Wherever possible the German endeavored to site their guns so that they would have a full 360° arc of fire. Coastal artillery was able to engage in either direct or indirect fire. In most cases, fields o fire had been carefully plotted so that nearly all guns were capable of blind barrage fire.

  2. The German employed both radar and visual methods of fire control. Control positions were often sited at a considerable distance from the guns. Communication cables were normally underground.

  3. In addition to coastal batteries, the Germans held a certain amount of mobile artillery in divisional, corps, Army and Army Group reserve. This was to be despatched to any assaulted sector to reinforce the fixed artillery. To accommodate a concentration of reserve artillery at any point along the coast, a large number of empty emplacements, armed only with light guns, were built. Heavier guns, gun howitzers and howitzers, from reserves further inland, could thus be emplaced quickly in any threatened sector.

  4. Coastal batteries, including howitzers and filed artillery were housed, with few exception, kin concrete emplacements from which only the muzzle of the gun protruded.7 The standard thickness of concrete pill-boxes and shelters was

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    6'6" in strongly defended areas and 3'3" in weak areas. Shelters for very heavy guns and for very important points were sometimes as thick as 10 to 15 feet. Reinforced concrete of the mat type, with 15 mm. rods at 10 and 12 cm., was the standard method of construction. Armour plate, though not widely used, was employed when available. It was considered preferable to concrete, because, being thinner, it permitted a wider field of fire. Steel cupolas and turrets, giving an all-round field of fire and coupled with overhead concrete protection for personnel, were common.

  1. The Germans made it a universal practice to provide all batteries, whether open or emplaced, with extensive underground reinforced concrete shelters for the protection of the crew and ammunition. These shelters were connected by undercover trenches. Coastal batteries were themselves turned into miniature strong points for their own local defense. Wire, mines, pill-boxes, anti-tank and even light field guns, usually surrounded them in proportion to their importance. The lightest batteries had little beyond wire and a few mines, while the heavy batteries of the channel coast were each the center of a major defensive position.

E. Disposition of Garrison Troops and Mobile Forces

  1. This massive skin of coastal fortifications was manned by four coastal Armies, consisting of some 41 divisions of static troops.8 Each coastal Army included two or three coastal Army Corps, while each Corps in turn was made up of two or three coastal divisional sectors. Frontages held by coastal divisions varied from about 25 miles, in Belgium and the Pas de Calais, to 40-50 miles in Normandy and to over 0 miles along the Biscay coast, depending upon the distance from Allied bases, the likelihood of invasion, the nature of the hinterland, and so on. Some two or three static divisions were stationed in the NEPTUNE Area itself, each defending approximately 40 miles of sea front.9

  2. The majority of coastal divisions were not up to full strength in men or equipment. They included a proportion of non-German personnel (e.g. Poles, Belgians, Dutchmen, etc.). They were, however, well supplied with concrete

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    defenses and were expected to fight well until driven from their fortifications. Coastal defense divisions ordinarily had only two reliable regiments,10 both stationed in the forward area. There were few, if any, regiments in reserve. Each coastal regiment normally had two battalions forward, and one in reserve. The reserve battalion was used as a standby for resting troops out of the line, and for immediate thickening up of an attacked sector. It was stationed so as to arrive in the battle area within two or three hours of the assault. There were four general types of coastal divisions:

    1. Some 16 infantry divisions were organized on a normal three regimental basis, but with a reduced scale of transport and liable to be called on to supply drafts for active fronts;

    2. About 8 lower establishment infantry divisions were on a two regimental basis, with reduced scale of artillery and transport;

    3. Some 13 static reserve divisions, whose primary object was the training of recruits, had to combine this function with coastal defense because of man-power shortage;

    4. Four G.A.F. Field Divisions, recruited from personnel who enlisted in the German Air Force, were being used in a purely infantry role as reserves for coastal defense forces.

  1. By mid-May 1944, the Germans had accumulated some 19 divisions of Mobile Reserves in France and the Low Countries.11 This force consisted of 8 Panzer, 1 Panzer Grenadier, and 10 Infantry Division. They consisted, for the most part, of armour and motorized divisions, refitting after service in Russia, or being reformed after destruction on the Eastern or Mediterranean fronts. They also included S.S. and paratroop divisions, some still in training, and others not up to full strength, in personnel or equipment, or both. But the greater part were full-strength and were rated good to high in combat efficiency.

  2. Prior to 1944, these divisions were usually transferred to active fronts, as soon as they were up to strength and

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    fully trained, In 1944, in view of the expected assault, the Germans kept their mobile reserve in the West as strong as the situation on the other fronts permitted. The role of the mobile reserves was to effect deliberate counter-attacks to throw any invading force back into the sea before it could penetrate the coastal defenses. The Germans intended to bring the first of these mobile divisions onto the scene within 6 to 12 hours after any landing.

  1. The mobile reserves were retained under the direct command of Army Group D, and were not assigned to any of the coastal Armies. Most of them were not centrally stationed, but were disposed at fairly regular intervals in communication centers some 20 miles inland. If any particular area was threatened, they were to be moved even closer to the coast. Troops were ordinarily billeted on the civilian population. Camps and barracks were avoided except in a few training centers. Units were dispersed over a fairly wide area but always along two or three main roads, to facilitate speed and ease of departure without the necessity for moving through a concentration area. In an emergency, the two divisions nearest the area assaulted were to make for it at once, by road if possible. The Germans planned to launch at least one division in counter-attack by the afternoon of D-Day.

  2. Mechanized divisions, except for those very far away, were scheduled to use roads. Tracked vehicles were to entrain, in case the distance to be covered was more than 120 miles. Other divisions were to travel by rail, unless forced by Allied air bombardment to use roads. To provide for such a contingency, the Germans had requisitioned enough civilian vehicles to be able to transport several divisions simultaneously.

  3. In addition to the mobile divisions, Army Group D also held a certain amount of mobile artillery, including railway artillery, motorized guns and a large quantity of wheeled coastal artillery, in a central reserve. German heavy flack weapons were also mobile and so designed as to be usable against aircraft or against surface targets.

  4. The Allies estimated that on D-Day the German dispositions of mobile reserves would permit them to reinforce the 5 static divisions, in and near the NEPTUNE Area, with a maximum of 3 mobile divisions,12 bringing total of 8 in

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    action on D-Day. These would include 4 static infantry defense divisions, 1 field infantry division and 3 armoured divisions. By D plus 3, the Germans were expected to be able to deploy an additional 7 divisions, making a total of 15 (4 static defense infantry divisions, 5 field infantry divisions and 6 armoured divisions.13 By D plus 6, they were expected to be able to deploy a further 6 divisions, thus making a total of 21, in the assault area. All of these figures represented the optimum rates. It was the best the Germans could do. This maximum would not be achieved however, if the Allied cover plan induced the Germans to delay the movement of mobile reserves or if Allied air forces impeded their movements. In fact, the Germans in June 1944 fell far short of these rates of reinforcement. The location of German divisions, the areas of responsibility of German armies and the optimum rate of German reinforcement into the Normandy area, are show on the appended sketches.13

F. German Naval Forces

  1. In November 1943, German naval forces (major vessels) consisted of:15

    1. Two battleships (one seriously damaged)16

    2. Two Pocket Battleships

    3. One aircraft carrier (unfinished)

    4. Two heavy cruisers

    5. Four light cruisers

    6. Thirty-seven destroyers (approximate -- excluding uncompleted and non-operational units)

    7. Eight-three torpedo boats (approximate, excluding non-operational units)

    8. Two hundred U-boats (approximate, excluding non-operational units).

  2. In March 1944, ANCXF estimated that:

    1. "Enemy surface vessels likely to be used against the assault were the following:

      1. Five destroyers

      2. Nine to eleven torpedo boats (including Eblings)

      3. Fifty to sixty E-boats

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      1. Fifty to sixty R-boats.

      2. Twenty-five to thirty M-class minesweepers.

      3. Sixty miscellaneous craft.

    1. "A further six destroyers and 10 torpedo boats might be sent from the Bight or Baltic, but if so, the enemy's heavy ships would have no screen should they put to sea.

    2. "130 U-boats operating from Biscay ports might, between D plus 4 and D plus 14, be reinforced to a total of about 200. They could work for a short time at a ratio of 60 percent at sea, losses up to 30 a month being made good from the partially trained Baltic reserve.

    3. "Up to 25 short-range U-boats (300 tons or less), in addition to the above could be sent from the Baltic to operate off our east and southeast coasts."17

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  1. The disposition of enemy forces between the Bight and the Bay of Biscay (inclusive) was as follows:18

      Heligoland Bight Ports Dann Helder to Dieppe Le Havre Seine Bay Cherbourg and Channel Islands Channel Islands to Brest Biscay Ports
    U-Boats -- -- -- -- -- 20 35
    DD's -- -- 1 -- -- -- 5
    Torpedo Boats -- -- 4 -- -- -- --
    E-Boats -- 30 -- -- 17 -- --
    R-Boats 10 55 -- 5 -- -- --
    "M" Class M/S 20 20 1 -- 3 15 50
    German LCG's 4 30 7 8 3 -- --
    Spernbrechers 8 3 -- -- -- 8 15
    M/S Trawlers -- 30 10 12 -- -- --
    Patrol Vessels -- 4 8 20 -- -- --
    Harbor Defense Craft 10 15 -- 45 -- -- --

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  1. Admiral Ramsay made the following estimate of the probable enemy naval reaction to NEPTUNE:19

    1. Once it is clear that invasion is taking place, it must be expected that the enemy will expend his forces ruthlessly in attempting to defeat it. His cruisers and larger ships may make diversionary sorties into the ATLANTIC, but their use in the Channel area is unlikely except as a desperate measure. His light surface forces will probably be used as directly as possible against the assault. They will probably be concentrated in the Channel and southern NORTH SEA area. These forces will probably restrict their attacks to the dark hours and periods of low visibility, operating on the flanks.

    2. His U-boats will probably be concentrated rapidly in the Channel and its western approaches and operated without regard to losses. In order to maintain the threat to the ATLANTIC shipping routes, U-boats from NORWAY and the BALTIC could relieve those moved into the Channel by about D plus 14 day.

    3. Evidence of Midget U-boats or fast small submersible craft is accumulating and (March, 1944) a small number may have reached the operational stage.

    4. Offensive and defensive minelaying by enemy surface vessels and aircraft is probable. New types of mines may be used."

    Mine laying was considered to be the enemy's most dangerous naval weapon.20

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G. German Air Forces

  1. The first line strength of the German Air Force on the Western front on D-Day was expected to be about 1,515 aircraft disposed as follows:21

      Long-Range Bombers Bomber Recce. Tactical Recce. Fighter Bombers Twin-Engined Fighters Single-Engined Fighters Coastal Total
    West and South of the Seine to 46° N. 70 35 10 -- 25 45 -- 185
    West of the Seine and Belgium 70 10 -- 30 185 65 -- 360
    Holland -- 10 -- -- 95 30 -- 135
    Northwest Germany 200 10 00 35 245 210 35 735
    Denmark and Norway, South of Trondheim -- 10 -- -- 10 40 40 100
    Total 340 75 10 65 560 390 75 1,515

    1. The close support force, available from this total for operations in the NEPTUNE area, was estimated at 590 aircraft, consisting of:

      Long-Range Bombers Recce Fighter Bombers Twin-Engined Fighters Single-Engined Fighters Total
      320 10 65 75 120 590

    2. The 320 long-range bombers included about 90 specialized (anti-shipping) aircraft, fitted for launching torpedoes and glider or FX radio-controlled bombs. These 90 might also be augmented by a further 60 aircraft at a later date, as an expansion of this force was known to have been made.

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    1. The above figures represented the maximum which the German Air Force would be likely to commit directly against NEPTUNE. The bulk of the remaining fighter force would be reserved for the day or night defense of Germany and of bases and communications in the west.

  1. A part of the long-range bomber force was expected to be used before NEPTUNE, for sea mining operations off the South and South East coasts of England. These operations were likely to be intensified when the Germans appreciated that preparations for a cross-channel operation were well advanced. Such operations would, however, be at the expense of the long-range bomber effort against targets in the United Kingdom. The maximum scale of effort, which the Germans were likely to expend during the three weeks before the operation began, was estimated to be the following:

    Sustained, per night 25 sorties
    Intensive, per night for 2/3 nights per week 50/75 sorties
    Maximum on one night 100/150 sorties

  2. The German bomber force was expected to operate mainly at night. In the early stages, however, a few daylight operations might be made, probably at first and last light. As this bomber force had had no experience of day operations, its efficiency in such operations was expected to be very low. The morale of the German bomber crews was slowly deteriorating. The single-engined fighter force was expected to be used mainly in a defensive capacity against Allied air forces and as escorts for day bombers and fighter bombers. A proportion of both single- and twin-engined fighters were capable of operating as fighter bombers or as ground attack aircraft, by daylight and possibly by moonlight. A proportion of the German single-engined fighters, equipped with rocket mortars, were available for attacking Allied landing craft, small shipping, and ground forces. Pilots, however, would lack experience and operational efficiency. Some of the German twin-engined fighters, with fighter escort, were also available for anti-shipping and ground attack duties.22 The German air forces enjoyed one

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    important advantage over Allied air forces. Their airfields were located much nearer the assault area than those of the Allied air forces.23

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Footnotes

1. Except where otherwise noted, all materials in the section on the enemy situation have been taken from: (1) XFPM 11, or 17 April 1944; (2) XFPM 12, of 26 December 1943; (3) ON 1, Paragraph 11 and 12; (4) ON 1, Appx. VII, Annex K; (5) ON 1, Appx VII, Annex D.

2. The approximate location of the various German divisions on the eve of the invasion, and of boundaries of German Armies in France, is shown in the sketch after Section 1 of this Chapter. (See CTF 122 NEPTUNE Monograph of April 1944, revised, Folios J, K, and L.).

3. During 1944, however, a last minute attempt had been made to tighten up the defense by constructing lines of field defenses on the first suitable high ground inland from the coast, but these were no more than support positions for the beach defense, intended to be used in sealing off any initial penetration made by the invading force. These filed defenses were unable to give direct support to the coastal crust, however, except in those few cases where the high ground came close to the coast.

4. The Germans had not constructed these before 1944. But in February of that year the placing of underwater obstacles on a large scale on open beaches in Northern France became a general policy. The progress of construction was continuous and fast. In one case seven staggered rows of stakes, 10 feet between units and 20 feet between rows, were inserted over a distance of 5,000 yards between 21st and 28th February 1944. In an other case, 2,300 yards of double row hedgehogs or tetrahedra were laid in four days at a spacing of 26 feet between units, and 10 feet between rows.

5. The obstacles were not connected by chains, cables, or wire. The fact that short stretches of different obstacles were often intermingled indicated the urgency with which the work was done. At one point, for instance, a line of Element C was moved down from a strong point at the back of the beach.

6. Few of them had an effective range as great as this, but, on the other hand, one battery in the Pas de Calais area had been known to shoot more than double that distance.

7. Prior to 1943-44, the Germans made it a practice to site the gun in an uncovered position. This was preferred to the pill-box proper as the open position gave a much greater field of fire. Nearby concrete shelter was provided for personnel who served a number of open fire positions. However, by 1944, the Germans had revised their scheme and were covering all fire positions with concrete as rapidly as possible. Pill-boxes and casemates were usually included in one master network which provided accommodation for personnel, ammunition, stores and so on.

8. Figures taken from CTF 122 NEPTUNE Monograph of April 1944, revised in May, folios J, K, L. These were obtained from FUSAG.

9. When the Caen sector was selected in August 1943, there was only one division in the entire sector. (See Appreciation and Outline Plan).

10. When they had a third regiment, it was usually composed of non-German troops.

11. See CTF 122 NEPTUNE Monograph of April 44, revised, Folios J, K, and L.

12. This would make a total of 8 divisions, which would be the maximum the Germans could deploy on D-Day. 3 static in the immediate NEPTUNE area, 2 static located very nearby and 3 mobile reserves. This 8 compared with 7 which the Allies would land.

13. Corresponding to the 15 German divisions on D plus 3, the Allies would have landed approximately 12 divisions.

14. These sketches were taken from CTF 122 NEPTUNE Monograph of April 1944, revised, Folios J, K, and L.

15. CCS 300/3 of 18 November 1943.

16. By D-Day both had become unserviceable. (See ###TF NEPTUNE Monograph).

17. ON 1, Para. 10.

18. ON 1, Appx. VII, Annex K.

19. ON 1, paragraph 12.

20. ANCXF report, Appx. 1.

21. The figures given here have been taken from ON 11, Appx. IV.

22. An appreciation of the size of German specialized anti-shipping forces available was hard to make, owing to the high degree of flexibility possible and to the use of many types of aircraft. In was clear, however, that all forms of attack could be met by available Allied air forces.

23. One main objective of Allied air forces was to disrupt German air fields within 150 miles of the assault area, and to make them unusable. Early construction of Allied air fields in Normandy was also a major objective. (See Chapter IV, Section #B and 3C.)

Transcribed and formatted by Charles Hall for the HyperWar Foundation