Between the first and the second World War the attitude in Denmark was dominated by the successful Danish neutrality policy in WW1. The Danish government felt confident that a friendly attitude towards Germany would prevent hostilities. As a result the Danish armed forces were reduced to a level where they had no deterrence value and the country could not be defended adequately.

When Germany invaded the Army counted 14.500 men. In 1939 some 30.000 more had been mobilised, but these had since been sent home again. In 1940 mobilisation did not occur in order to prevent provoking Germany.

Operation Weserübung
Germany on its part didn't really care much for Denmark in itself. The objective of Weserübung, the attack on Norway and Denmark, was to get access to naval bases on the Norwegian coast and to prevent the allies from blocking the German access to the Swedish iron-ore, which was shipped through the Norwegian ice-free ports to Germany.

In order to obtain air support for the Norwegian attack control of airfields in northern Denmark was necessary. Various German initial plans for the attack required only access to key strategic areas in Denmark without attacking the entire country. The Altmark affair on 16th February 1940, where the British boarded a German ship in Norwegian waters to free prisoners, convinced Hitler that Norway and Denmark were neither willing nor able to protect their neutrality against allied aggression, and as a result it was decided that the entire country should be conquered.

When the attack came the Danish were unprepared. The attack was the first in a new era of warfare where surprise was sought by not applying diplomatic pressure in advance. Warnings had been received from an anti-nazi leak in the German intelligence service, but these were ignored and only few units were on alert.

The government was presented with the German ultimatum in the morning of the 9th of April 1940 and protested, but accepted while bombers flew over the city. Due to the earlier neglects no effective opposition was possible and the aim of the government was to reduce the suffering to a minimum. While this attitude did get Denmark through the war with a minimum of casualties it nearly resulted in the exclusion of Denmark from the league of allied nations.

The German attack was executed to quickly take all the key strategic areas in possession. The border itself was crossed several places. Seaborne landings were conducted in the capital, in other major ports and at the main crossings between the Danish islands. The first airborne landings in the history of warfare were conducted at Masnedo fortress controlling the bridge from Falster to Zealand and at Aalborg airbase.

Such was the German urgency that the secret of airborne units that should have been kept to the western offensive was revealed. Another innovative part of the plan, for that time, was that all parts of the attack in both Denmark and Norway was conducted at approximately the same time to achieve surprise. Only in a few areas did any fighting occur during the 4 hours from the attack started to the capitulation was effective. The southern part of the peninsula saw resistance by the few units in position and the Kings castle in Copenhagen also saw fighting. Only 11 Danish soldiers were killed during the attack.

The Danish resistance movement was very limited until the turning points of the war in 1942. From then on it expanded rapidly. Its main operations included industrial sabotage and railway sabotage to hinder troop movements from Norway. While the operations did have an economic impact on Germany it never reached a scale where partisan activities took control of larger areas.

The flat and open Danish terrain is not well suited to large-scale partisan operations. However small its actual effect was, the resistance movement showed the world that the Danish population did not wish to be ruled by Germany. This, and probably more important, the 5000 sailors that joined the allied merchant fleets, were the main reasons that Denmark ended the war as an allied country.

Greenland
Another important contribution to the allied war effort was made by the Danish envoy in Washington. He did not recognise the government in Copenhagen during the war and acting on his own he granted the US basing rights in the Danish controlled Greenland. This allowed the transfer of short-range aircraft to Britain via Greenland and Iceland.

In addition to the US bases, meteorological stations in Greenland were vital to making accurate weather forecasts for Europe. The occasion where this was most important was when the decision was made to invade Normandy on 6th June 1944 as the forecasts predicted that the storm would end - information that was not available to the Germans. The Germans tried to get meteorological stations operating in Greenland, at first Danish manned and in 43 and 44 manned with German personnel.

The German attempts were prevented by Danish and US patrols in Greenland. During the war the main contribution of Denmark to the German war effort was its agricultural exports which covered a large percentage of the German needs. In addition 100.000 workers went to work in German factories and with the permission of the government 7.000 Danish soldiers volunteered to join the German units in Russia.

From 1942 the threat of an invasion from the west was clearly felt in Denmark. The northern end of the Atlantic Wall fortifications was build on the west coast using Danish labour and on D-Day 220.000 German soldiers were stationed in Denmark. The Germans thought an invasion here was a possibility, but not a very likely one. The reason they thought it was not very likely was because of the German air superiority in the area. The Allies came to the same conclusion, the need for air power meant the invasion had to be made in France.

When the German surrender came, fighting had not yet reached Denmark, which was again spared from the worst. The only major fighting occurred on the island Bornholm where the German commander would only surrender to a British representative and no such was present. While the rest of the country unknowingly celebrated the liberation, Russian planes bombed the harbour towns causing great material damage and killing 9 people. The island was then invaded by the Russians, who kept it for a year before returning it to Denmark.