Hi, a few years ago one of my teachers brought a box to school that she found in her grandpa's house after he passed away. It had a diary and several items from world war 2 like a dagger and documents/newspapers. In the diary talked about when he was part of a special force that's mission was to help Norwegian forces kill nazis after they had been allowed to travel through Sweden.
As I understood it they only did night missions and used knives and piano wires to kill while they were sleeping.
This story really stuck with me and I would love to hear if there's any more information about this since I could not find much online.
Do you have a time frame when this happened?
There were Swedish troops that against orders crossed the border individually to fight the nazis during the invasion April-June 1940 - these men included a part of SFK, the volunteers that had fought for Finland against the Soviets just before.
Swedish military intelligence, G-sektionen (from 1942 known as C-byrån) maintained close contacts with the Norwegian resistance and helped hide, arm and train Norwegian agents as well as let them transit through Sweden into Norway and back after training with SOE in Britain. Unfortunately, C-byrån purged its archives of any names before turning it over to Krigsarkivet in 1967, so we will not be able to verify things independently there.
However, as far as I know, c-byrån did not use agents as such - they gathered intelligence through spies and informants. For example, when the Germans unloaded maps of Sweden in Norway, the Norwegian toll official that handled the shipment sent information on to C-byrån, leading to the Swedish military knowing that the Germans had 1:100 000 maps over Sweden the day after they were unloaded 1943-04-05. Another example is when the Germans moved the 25. Panzer-division in May 1943, from the area of Oslo to the area of Trondheim, the new location of the division shows up in Swedish staff reports only two days after the division had finished moving.
Sweden did raise three corps Jäger battalions in line with the Finnish Sissi long range patrol units and they were trained to operate behind enemy lines, to destroy infrastructure, lay ambushes, link up with resistance, do long-range recoinnasance on the ground and so on in the Swedish doctrine of the "free war" (operating without continious lines and contact with own forces). Although these units would do long range patrols and act behind enemy lines and use guerilla tactics, they were uniformed and armed troops according to the Geneva convention and did not use knives and piano wire to kill people in their sleep.
The final candidate would be someone associated with the Norwegian "police" (in reality regular infantry) battalions trained and equipped in Sweden from volunteers among the Norwegian refugees in Sweden.
If you have more information on the timeframe, nationality, any units the grandpa of your teacher served in, and so on, I could dig further.