Danish version 

The Author  
 Map and Overview
Fortification overview

Defence of Copenhagen
The Persons behind
The  Mobilisation 1914
Attack against Denmark

 The Northern Defence Line
The Forts
The Batteries
The Flooding
The Positions

 The Naval and Coastal Forts
The 1. Defence Line
The 2. Defence Line
The 3. Defence Line

 The Western Defence Line
The Principles
 The Profile
The Caponiere
The Batteries
The Storing Facilities

 The Tune Position
Modern Warfare
The Aerial War
The Position
The Mosede Fort
The Foxholes
The Galleries
The Trenches     
The Artillery
The Air Defence    
The Camps and Barracks
Other Facilities
After WW I
The Present Remains



The Fortifications of Copenhagen

The Threats against Denmark


  Was there a threat against Denmark during WWI?

One can do a lot of guessing, and in my opinion there was a risk. Especially in the beginningof the war. Denmark situated as a cork in the Baltic and considered an open flank for Germany, was a possible target. The question is, if Germany was willing to use a great amount of resources to march into Denmark.
In order to maintain its neutrality, Denmark had mined some of its waters after a German demand. It would be against German interest if these mines were removed, giving England access to the Baltic.Just the threat of this could justify a German invasion.
The German Navy was very anxious  to invade. The Army however, was more reluctant.
Even at that time, the capitol was the key to the country, and therefore an attack against Copenhagen and the defense line was possible.

To have an opinion on the possibility, we know that a German attack-plan was made. It was found in the German Marine archives in Freiburg (fall J - Plan J)

We can use the judgments of the generals and other officers at the time and we can compare with the German attacks on Liege, Namur and Antwerp. The three defense lines mentioned above was demolished by German siege artillery twice as power-
full, as any fortress was build to resist or anybody except the Germans knew about.

3 scenarios were possibel.
Occupy the city with infantry, siege the city to surrender or shell it to surrender.

Scenario 1
Occupying the city would require at lot of infantry and artillery. Equipment, that was desperately needed on the western front. Further more it should be remembered, that it took the Germans 2½ month to crush Dybbøl in 1864. The construc-
tions of Dybbøl were not even dug in or made of concrete.
Normally it's considered that it takes 3 times so many men to attack than to defend. Denmark had 40.000 men on the Copenhagen defense line. Did Germany have the ability to spare 120.000 men and logistic to move them with the needed artillery. ? Were they willing to risk their major naval forces ?
I think Denmark was to inferior for such an operation.

Scenario 2:
Another scenario was to avoid the defense line with artillery and shell the capitol form outside.
That way they could force the city to surrender without confronting the defense. Germany had the
ability with the 30,5 and 42 cm guns. 
But transporting the biggest guns Germany had very little of (6 pieces of the 42 cm gun in 1914 and 20 in 1916) to Denmark, demanded a lot of railroad and harbor facilities. Facilities that had to be occupied first: 

Scenario 3:
An old-fashion siege of the city, with at ring of warships, infantry and artillery to starve the city.
The naval blockade would confront the naval- and coastal fortresses. This scenario also demanded
a great amount of military resources, resources Germany probably could not spare.


 Artillery to be expected:
 * Caliber=diameter of the shell

   Caliber Type  Range Shell weight Targets
  13 cm.  Siege gun 14 km. 40 kg.  Against distant uncovered targets
  15 cm        Like the Danish guns, but later improved
  21 cm Haubitz (Mörser) 9,7 km. 120 kg  Very accurate "Haargenau". Shocked rather than blasted. light constructions and
 armoured cupolas.
  28 cm Haubits 10 km. 340 kg.  Schwerer Küsten-Mörser. Very curved trace.Originally made to penetrate deck in a 90
 degree angle made it very usefull against  hidden constructions and bunkers.
  30,5 cm Haubits 11 km. 330 kg.  Kurze Marine Kanone. Very effective against armour. Penetrated even heavy armoured
 targets and
caused serious destruction inside the constructions.
  42 cm  Haubits
9-14 km. 810-1160 kg  Known as Dicke Bertha, named after Krupps wife. Used where nothing else was
 effective. Known to have penetrated 6 feet of earth, 9 feet of concrete and finally
 penetrated 2 feet of concrete (without detonating) on an older french fortress.

   Germany had a very litt   of the42 cm, 11 pieces of the 30,5 cm. and 4 pieces of t

                                                                                                                         21 cm. Mörser
   28 cm Haubitz "Schwerer Küsten Mörser"
                                         30,5 cm Haubitz "Kurze Marine Kanone"

               42  cm. Mörser "Dicke Bertha"

                    The heavy effect the German 30,5
                      and 42 cm. guns had on the constructions
                      was due to the fact, they were  build to
                      resist  shells loaded with black powder.
                      In the meantime high explosives had been


Armoured cupola in Liege blown away after
         a hit from a 42 cm. artillery piece,
  The biggest Danish artillery in the ground defense, were 15 cm. steel guns on the southern defense line and 15 cm steel guns in armored cupolas on the forts.

 The lesson from the barrage of Liege would be, that fortresses with infantry-positions between them to prevent the enemy to observe the shelling from close range and keep the artillery on the distance was the best weapon against the big siege-guns.
This means, that the southern front had very little chances against the heavy artillery, except for the fact, that it would be very difficult to observe the effect of the barrage.
The Northern front would have had better chances, with some exceptions. The old "tall" fortresses Lyngby and Garderhøj were very visible on the horizon, and therefore easy to artillery-observe against from the distance.
They would probably have ended up like the fortresses of Liege.  
The low profile fortresses Bagsværd, Gladsaxe and Fortun were more likely even opponents.

These experiences were essential for the construction of the "Tune-position" in 1916.

The massive infantry the southern front was effective against and the heavy artillery never came.
The German attack plan against Denmark "Fall J" was given up, simply because there wasn't troops and artillery enough just for closing an inferior open flank in the north. Denmark remained neutral, and the defense line never tested or destroyed.