Sabotage. Geographic conditions did not favour partisan warfare in Denmark, but sabotage proved the main problem undermining the German occupation. Here the facilities of the Riffelsyndikatet burning after the sabotage action on 22 June 1944.

On 9 April 1940 at 4:15 in the morning the hitlerite Wehrmacht launched operation Weserübung Süd (Weser Exercise South) and attacked Denmark. After a short resistance, having 16 killed and 23 wounded, the Danish army ceased fights. That small country (43, without forests or mountains, inhabited by 3,800,000 people, was occupied so quickly and unexpectedly that many Danes did not realise it until they left for work in the morning and saw German troops in the streets.

The Germans had announced in the official declarations that they had no hostile intentions towards the Danes, and that the Wehrmacht came to their country solely to protect them from a British aggression. They left in power the legitimate government, which was forced to accept this peculiar condominium. The German ambassador, Cecil von Renthe-Fink, was appointed the Reich's plenipotentiary with the Danish government; the Danish embassy in Berlin worked "as usual". King Christian X had his daily horse rides, during which he was receiving greetings from his subjects. It was a visible symbol of Denmark's sovereignty, apart from the residual army and the navy. In the beginning of the occupation the Germans tried to propitiate the Danes, whom they regarded as a part of the Germanic race. Yet, the little Danish "canary" did not let the German vulture to have it devoured or tamed.

However, when it comes to mobilization of the Danish people for armed struggle against the invaders, objective factors did not favour it to the degree as high as other countries saw it. The Danes were in general pacifists - their country did not know war for 80 years - with materialist and loyalist mentality. Together with the occupation, there had become active fascist forces - the National Socialist Workers' Party of Denmark (Danmarks Nationalsocialistiske Arbejderparti - DNSAP), founded in 1930, led by Frits Clausen, and the Danish People's Party (Dansk Folkeparti), founded in 1941. On the other hand the factor that objectively favoured resistance was proximity of neutral Sweden, reachable by boat, and Swedish authorities' friendly attitude.

So, the beginnings of the resistance to the invaders were difficult. The first political force to formulate its programme of mobilization for resistance was the Communist Party of Denmark, which as early as on 15 April 1940 appealed to all its sympathizers to remain vigilant and continue efforts for political and social liberation of the country and the Danish people. In the summer of 1940 a lot of leaflets had been circulating around Denmark; they called upon passive resistance and sabotage. Also at the same time there was circulated so-called "Ten Commandments for Danes":
  1. You must not go to work in Germany and Norway.
  2. You shall do a bad job for the Germans.
  3. You shall work slowly for the Germans.
  4. You shall destroy important machines and tools.
  5. You shall destroy everything that may be of benefit to the Germans.
  6. You shall delay all transport.
  7. You shall boycott German and Italian films and papers.
  8. You must not shop at Nazis' stores.
  9. You shall treat traitors for what they are worth.
  10. You shall protect anyone chased by the Germans.
  11. Join the Struggle for the freedom of Denmark!
First issues of clandestine literature have been distributed. They proved that there were individuals in the Danish society, who, by calling to the resistance, as passive as it had to be, stood for the honour and freedom of Denmark. Among them was Vilhelm la Cour, a historian, social activist and the editor of a provincial magazine Grænsevagten (The Borderland Watch), in which he challenged propaganda disseminated by German newspapers. Towards the end of 1940 he initiated a series of lectures, during which he denounced the government's concessions to the invaders.

Another person, who did not accept the Danish government's policy towards the Germans was the ambassador in the USA, Hendrik Kauffmann, who yet in April 1940 organized the movement Free Denmark (Frit Danmark). Others thought about protecting the Danish youth from the influence of the Nazi propaganda. Under the guidance of Hal Koch, a professor of Church History at the University of  Copenhagen since 1937, there was established the Danish Youth Association (Dansk Ungdomssamvirke). Strictly speaking, it was not an underground organization, and Hal Koch never considered himself a part of the underground movement despite several approaches, notably from Frode Jakobsen (social democrat) and Aksel Larsen (communist). Instead, Hal Koch thought about the Danish Youth Association as a forum to rise political awareness of the Danish youth, and educate them in principles of democracy. The Danish Youth Association existed till 1946. Another organization, rallying youth for resistance was the Danish Unity (Dansk Samling) founded by the journalist Arne Sørensen yet in 1936.

Another form of national resistance, unknown elsewhere in the occupied Europe, was born by initiative of pastor Axel Bang from Aalborg. On 4 July 1940 he organized an assembly attended by about 1,500 people, who sang Danish national songs. The Germans did not dare to intervene. Encouraged Danes continued the action, and on 1 September as many as 35,000 Danes were singing in the streets of Aalborg and few days later - 40,000 in Copenhagen. Altogether, in 1940 alone, as many as 740,000 Danes took part in massive patriotic manifestations called allsang.

In November 1940 Admiral Erich Raeder demanded that Denmark handed over 12 torpedo boats. Both the king and the admiralty protested, but under the German pressure they had to yield 6 ships. That fostered increase in anti-German feelings in the Danish society.

However, anti-German feelings did not mean yet the Danes' willingness to start an armed struggle with the invaders. There is a long way from reluctance to fight. For example, till 1943 the Danish police without reservations used to hand over shot-down British airmen to the German authorities, while civilians were not in hurry to shelter them. At best they would get on some passive demonstrations, like on 26 February 1942 in Aabenraa, where the Danes laid a wreath with red-and-white sashes on the graves of six Polish airmen; what is interesting - upon a consent of the German authorities.

After the invasion of the Third Reich on the Soviet Union the German authorities demanded that the Danish government arrested communist activists and anulled mandates of the three communist members of the Danish parliament; 296 communists were imprisoned in the camp Horserød. The Communist Party of Denmark (Danmarks Kommunistiske Parti - DKP) was banned. The Danish government also had to consent to formation of a unit of volunteers to fight along the Germans on the East front. That unit was named the Free Corps Denmark (Frikorps Danmark) and recruited between 6,000 and 10,000 volunteers (1,500 in active service). The Free Corps Denmark was included into the structures of the Waffen-SS; its commander was first Lt.-Col. Christian Peder Kryssing, and later Capt. Christian Frederik von Schalburg. More Danish fascists served in so-called European SS formations like 5th SS Armoured Division Wiking, formed in 1940, and 11th SS Armoured Grenadier Division Nordland.

On 25 November 1941 the Danish ambassador in Berlin signed the Anti-Comintern Pact, and the "official" Denmark joined the "anti-bolshevik crusade", to the disapproval and protests of the Danish society. After all the "unofficial" Denmark had more and more to say. More and more clandestine publications circulated the country. The most popular one was the newspaper De frie Danske (Free Danes), published by a group of journalists. At the turn of 1941 and 1942 a conservative politician John Christmas Møller made an agreement with the communist leader Aksel Larsen and on 9 April 1942 started publishing the clandestine magazine Frit Danmark (Free Denmark), the main organ of the underground organization with the same name. All and all, during the occupation, as many as 600 clandestine publications were distributed in 26 million copies.

Gradually, the Danish underground undertook more active resistance to the German occupation. Main roles there played Danish patriots operating from Great Britain. The British Isles became the centre of organizing resistance of the European nations, including the Danes. On 30 September 1940 there was created the Danish Council (Dansk Råd), and in October - the Danish section of the Special Operations Executive (SOE) headed by Lieutenant-Commander Ralph Hollingworth. Although official Anglo-Danish relations were severed, the British did not lack contacts with the Danes or information from Denmark. Officers of the Danish intelligence were passing military information to the British intelligence through journalist Ebbe Munck, a reporter of the newspaper Berlingske Tidende accredited in neutral Sweden. There, in November 1940, Sir Charles Jocelyn Hambro, a banker, cricket player and a British intelligence agent, contacted Munck, making the beginning of a fruitful co-operation.

Among the first organizations to undertake active sabotage was the Communist Party of Denmark (Danmarks Kommunistiske Parti - DKP). The first sabotage group, named Communist Partisans (Kommunistiske Partisaner - KOPA) was organized in February 1942. As it grew in numbers, absorbing many volunteers, who were not communists, the organization changed its political image and name: it became known as the Civil Partisans (Borgerlige Partisaner - BOPA). The core of its cadres was made of the veterans of the International Brigades of the Spanish civil war. They started their operations yet in 1941, and since then their number grew every year: 19 sabotage actions in 1941, 122 in 1942,  969 in 1943, 867 in 1944, and 687 in 1945.

In the beginning of 1943 SOE parachuted to Denmark its agent, a writer Flemming Muus, who became the chief of the SOE operations in Denmark. Muus made contacts with BOPA and made agreement concerning transferring of weapons, explosives and instructors to the occupied country.

In April 1943, for the first time during the occupation of Denmark, German authorities sentenced a Dane (Hans Pedersen) to death for sabotage in mechanical workshops working for the Germans. It was the precedent that stirred the Danish society and augmented anti-German resentments. A wave of strikes swept across Denmark. On 9 August took place the first general strike - it happened in Esbjerg (east Jutland) in response to introduction of the martial law. On next days broke out strikes in Odense and Aalborg where clashes with the German soldiers took place. Although there were killed and wounded, strikes did not extinguish, bud spread all over the industrial centres of Denmark.

On 29 August the Germans introduced martial law in the whole Denmark. It opened a new chapter in the history of the German occupation of Denmark. The Danish government ceased to exercise its authority in Denmark, and all powers went to the Wehrmacht. Local administration became strictly bound with activities of the collaborationist organizations. The Danish army was disarmed, and its officers were interned. As the Germans attempted to seize the Danish navy, it received orders to sail to the neutral Sweden; when it failed, Danish ships were scuttled. More than 200 people were arrested upon suspicions in subversive activities. While evaluating the impact of those events on Denmark, Møller remarked that since then Denmark as a country, and the Danes as a nation had stood geared with all other conquered and occupied nations.

When the legitimate government ceased to function, nothing stood in the way of organizing a central authority of the resistance movement. On 16 September 1943 was brought into being the Danish Freedom Council (Frihedsrådet), which became the actual underground authority in Denmark. It constituted of 6 representatives of various political organizations of the Danish underground: Mogens Fog and Carl Adolf Gottlieb Bodelsen (Frit Danmark), Børge Houman and Alfred Jensen (Communist Party), Frode Jakobsen and Erik Husfeldt (Ringen party), (Arne Sørensen (Dansk Samling), Aage Schoch, and Ole Chievitz. Also Flemming Muus became a member the Freedom Council later. The Freedom Council was promptly recognized in London, and since December 1943 Danish ships seized by the Allies were allowed to sail under the Danish flag. Also in December the command of the army and navy recognized the Freedom Council as the supreme Danish authority until making a new government. That was practically the end of the "official" Denmark. From then on only the underground Denmark spoke for the Danish nation.

The Freedom Council resolved that its most important task - and London also demanded that move - would be creation of an underground armed force. By 18 January 1944 the Freedom Council formed the Military Committee, whose task was to organize armed resistance and co-ordinate its actions. The command of the armed resistance was entrusted to Gen. Ebbe Gørtz. Armed operations had commenced very soon. In April, Danish sailors immobilized 450 German ships; on 3 June more sabotage actions took place in the shipyards of Svendborg. On 6 June BOPA fighters attacked and blew up the Globus plants in the outskirts of Copenhagen, where aircraft and rocket parts were produced. For that action the commander-in-chief of the Allied expeditionary forces in West Europe, General Dwight Eisenhower, personally congratulated the Danish resistance. And on 22 June a 100-men partisan detachment blew up major Danish munitions works Dansk Industri Syndikat A/S (Riffelsyndikatet).

On 24 June a general strike began in Copenhagen after the Germans forbade to lit traditional bonfires for St.John's Eve. Shops were closed, transport was interrupted, and riots erupted. The commander of the German occupation forces in Denmark, Gen. Hermann von Hanneken, introduced martial courts, the Higher Leader of SS and Police, SS-Obergruppenführer Günther Pancke, ordered to execute eight patriots, and the Reich's plenipotentiary Werner Best sent the corps of the "Danish volunteers" to Copenhagen to suppress the strike. The Freedom Council appealed to refrain from violence, and simultaneously voiced demands to withdraw the "Danish volunteers" and lift the martial law. In the beginning of July the strike extended to the other regions of the country, engulfing 22 towns. On 5 July, after the Germans had to yield to the patriots' demands, the Freedom Council called to end the strike. That general strike in June and July 1944 was an important factor uniting the Danish people in the struggle with the fascism.

On 19 September 1944 the Germans launched the action of liquidation of the Danish police (about 10,000 men), which had been in service since the beginning of the occupation. The entire administration was arrested, and about 2,000 policemen were sent to the concentration camps. Many policemen joined the underground; the Germans had not even realised, what a reinforcement was it to the resistance movement.

The last months of the occupation of Denmark (spring 1945) were marked by the intensified sabotage on the railways, which prevented transfer of the German troops from Norway to the European continent. Out of 1,810 sabotage actions on the Danish railways 1,301 took place in 1945. As many as 119 trains were derailed, and 58 locomotives were damaged. Altogether 2,700 sabotage actions were carried in Denmark during the occupation. The numbers of the resistance fighters at the end of April 1945 reached 47 thousand people.

On 5 May 1945 an Allied mission Civil Affairs with the British General Richard Dewing and the Danish Colonel Gustav Rasmussen, and a company of parachutists landed in the airport Kastrup near Copenhagen, where they met representatives of the Danish resistance movement. On 7 May the troops of the 1st Parachute Brigade and the Royal Dragoons Regiment without resistance crossed the Danish land border, while Soviet troops landed on the Bornholm Island in the Baltic Sea after a heavy bombing of its German garrison. The occupation of Denmark was over.