What Hannevig built in the Telemark mountains was not a regular military unit but something more like a militia assembled from whatever was available. He called a full mobilization in the area, and at its peak the force numbered around 300 men, though the count shifted constantly as volunteers arrived and departed. The weaponry he had stolen from the depots was substantial for an improvised force: Krag-Jorgensen bolt-action rifles, Madsen light machine guns, Colt M/29 heavy machine guns, and 81-millimeter mortars. They also had mines and explosives for destroying bridges and roads -- not to win battles, but to buy time. The plan was straightforward: prevent the German forces from advancing westward through Telemark and Setesdal, and hold the line long enough for Allied reinforcements to break through from the west coast.

The fighting around Vinjesvingen unfolded as a series of small, sharp engagements rather than a single pitched battle. Hannevig's men used the mountain terrain to their advantage, setting ambushes along the roads that German formations needed to use. They blew bridges, mined roads, and attacked with small arms and improvised explosive devices before withdrawing into terrain they knew better than the invaders. The strategy was classic guerrilla warfare: make the enemy pay for every kilometer, force them to deploy disproportionate resources to clear the route, and disappear before they could bring their superior firepower to bear. German losses in the area were considerable -- far more than the size of Hannevig's force would suggest.

The main battle came between 3 and 5 May 1940. By then, the Germans had recognized that the Vinjesvingen position was a genuine obstacle and deployed large forces to eliminate it. For three days the fighting intensified, with Hannevig's 300 volunteers facing a professional military that had already conquered most of the country. But the strategic picture was darkening beyond repair. Southern Norway was lost. The Allied task force at Andalsnes, which was supposed to push inland and link up with Norwegian forces like Hannevig's, would not break through. When this became clear, Hannevig faced the hardest decision a commander can make: he initiated negotiations for surrender, knowing that continued resistance would cost lives without changing the outcome.

The Battle of Vinjesvingen carried enormous symbolic weight -- but almost no one knew about it while it was happening. The fighting in Telemark was remote, communications were severed, and the rest of occupied Norway had no way to learn that a force of 300 men was still resisting in the mountains. It was only after the war ended that the full story emerged, along with the parallel stand at Hegra Fortress in Trondelag, which held out until 5 May as well. Together, Vinjesvingen and Hegra represented the last Norwegian resistance in southern Norway before the focus of the war shifted north. For Norwegians living through five years of occupation, the later discovery that someone had fought back -- had stolen weapons from under the Germans and held a mountain valley for weeks -- provided exactly the kind of moral boost that the darkest years had demanded.