Norwegian resistance to the Nazi occupation of Norway from 1940 to 1945 took several forms:

• The initial defense in Southern Norway, which was largely disorganized, but succeeded in allowing the government to escape capture
• The more organized military defense and counter-attacks in parts of Western Norway and in Northern Norway, aimed at securing strategic positions and the evacuation of the government
• Armed resistance, in the form of sabotage, commando raids and other special operations during the occupation
• Civil disobedience and unarmed resistance

See also Weserübung and Nazi occupation of Norway

Initial defense

After a longstanding policy of disarmament after World War I, the Norwegian military was largely underfunded and undertrained by the late 1930's, though some politicians across the political spectrum had advocated strengthening the country's defense capabilities. As a result, forces in Southern Norway were largely unprepared for the invasion, and the German invading army met little initial resistance landing in Norway.

One notable exception was the sinking of the German cruiser Blücher at the sound at Drøbak, which delayed the capture of Oslo long enough for the government to escape the capital.

There was also spirited defense at other locations, including Midtskogen, but these were largely the result of improvised missions by isolated military units and irregular volunteers. The battles slowed down the German advance by several days, allowing the Norwegian government to evade capture and conduct critical constitutional business.

Counter-attacks

Several Norwegian military units that had mobilized as a precautionary measure in the Winter War in Northern Norway, and in cooperation with Polish and British forces launched several counterattacks with moderate success. Allied forces had several successes in Northern Norway, but were redirected for the ultimately futile defense of France. While Northern Norway ultimately fell, efforts there allowed the Norwegian government, including the royal family, to escape and maintain the legitimate government in exile, as part of the Allies. While stationed in London, the government contributed Norwegian forces to the Allied effort and ordered the Norwegian Merchant Fleet to assist in transportation. It also created apprehension in the Nazi leadership that Allied forces might try to recapture Norway to deny German naval units access to the North Atlantic, tying up several hundred thousand forces that otherwise would have been deployed to other fronts.

Armed resistance

Although Norway did not see major battles beyond those in Narvik, a number of military operations served to subvert the Nazi authorities and contribute to the larger war effort. Milorg started out as a small sabotage unit and ended up building a full military force in time for the liberation. Company Linge was a special operations unit that specialized in coastal insertions and combat.

There were repeated raids in Lofoten, Måløy, and other coastal areas.

Norwegian spotters aided in the destruction of numerous German warships, such as the Bismarck and the Tirpitz. The Norwegian resistance also smuggled people in and out of Norway during the war, through Sweden or by fishing boats to Shetland (referred to as the "Shetland bus"). A number of saboteurs (most notably Max Manus and Gunnar Sønsteby) destroyed ships and supplies. Perhaps its most famous achievements were a series of operations to destroy Norsk Hydro's heavy water plant and stockpile of heavy water at Vemork, crippling the German nuclear program (see: Norwegian heavy water sabotage). The Germans attempted to stifle Resistance activities and executed several innocent Norwegian men, women and children in retaliation after any Resistance act. Probably the worst act of reprisal was the assault on the fishing village of Telavåg in the spring of 1942.

Intelligence gathering within occupied Norway was very much needed for the allied forces, and several organisations were established for this, the largest and most efficient was called XU. Established by Arvid Storsveen, its basis were students from the University of Oslo. One interesting fact was that two of its four leaders were young women, among them Anne-Sofie Østvedt.

Civil disobedience

Of lesser military importance was the distribution of illegal newspapers (often with news items culled from Allied news broadcasts; possession of radios was illegal). The purpose of this was twofold : It counteracted German propaganda, and it maintained nationalistic, anti-German feelings in the population at large. It might also be argued that this activity absorbed German resources out of proportion to the actual effects.

Finally, there was the attempt at maintaining an "Ice Front" against the German soldiers. This involved, among other things, never speaking to a German if it could be avoided (many pretended to speak no German, though German skills were then almost as prevalent as English now) and refusing to sit beside a German on public transportation. The latter was so annoying to the occupying authority that they made it illegal to stand on a bus if seats were available.

Towards the end of the war, the resistance become more open, with rudimentary military organizations set up in the forests around the larger cities. A number of Nazi collaborators and officials were killed - and those collaborating with the German or Quisling authorities were ostracized, both during and after the war.

A symbol of the Norwegian resistance was wearing a paper clip on a lapel; an innocuous item, the paperclip was assumed to be a Norwegian invention, and represented uniting against the occupation.

The Norwegian Resistance museum, at Akershus fortress, Oslo, gives a good impression of the activities of the Norwegian resistance movement.

The events were also the subject of a computer game modification Norwegian Resistance, a total conversion that requires the Forgotten Hope mod and Battlefield 1942.