Considered an essential part of the Atlantic Wall in anticipation of an Allied invasion, the fortifications in Norway were primarily based around coastal artillery, but also included elements of anti-aircraft batteries, and battle tanks and infantry forces. There were as many as 400,000 German troops in Norway during the occupation, a large proportion dedicated to the defense of the Northern flank of the Atlantic wall.
The scope of Festung Norwegen originally included the entire coastal perimeter of Norway, from the Oslofjord around the southern coast and to the border with the Soviet Union. Part of the invasion plan for Norway included immediate deployment of German coastal artillerymen in Norwegian batteries, around the main cities of Horten, Kristiansand, Stavanger, Bergen, Trondheim, and Narvik.
An extensive network of coast artillery batteries with heavy (>15.5 cm), medium (12-15.5 cm) and light (<12 cm) ordnance was set up around the entire coast. These were typically placed so as to cover approaches to main population centers and likely landing sites. The batteries were also generously equipped with close combat weapons, such as machine guns and small firearms. By the end of the war, there were 221 batteries along the coast, under either Kriegsmarine or Heer command. There were also anti-aircraft artillery (Marine Flak) batteries in Kristiansand, Bergen, Trondheim, Bogen, and Harstad; these were armed with 88-mm pieces. The tanks available for the German defence were Panzer IIIs (50 mm L60 and 75 mm L24) and Sturmgeschütz IIIs (75 mm L48).