At the end of WW2 the Soviet Union ensured that many of their neighbouring countries fell under the Soviet sphere of influence, either by occupation, annexing land or installing communist governments. However, after liberating Northern Norway, the Soviet Union pulled out all their forces only a few months later. Less than four years after that, Norway was a founding member of NATO and in clear opposition with the Soviet Union.
Why didn't the Soviet Union occupy Northern Norway, annex bordering regions or Svalbard, or ensure that they had some influence over Norway by any other means?
I found this old answer by /u/dlamontagne to the same question. However, the answer is rather short and contains a dead link. I believe the link is supposed to be to this paper from 1994.
This paper shows that there was discussion among Soviet officials regarding Norway, and even a proposal for a "border adjustment" in the north (page 15). But the reasons the Soviets dropped all these plans doesn't seem so clear to me. The paper mentions a lack of coordination between foreign policy-makers and the military (page 17). It also mentions that Molotov realised "a Soviet initiative along the lines proposed by Zhdanova, Vetrov, Dekanozov et al. would have repercussions far beyond the Soviet-Norwegian relationship." (page 18). But repercussions far beyond the Soviet-"insert-any-other-Soviet-occupied-country" relationship doesn't seem to have stopped a Soviet occupation of other countries after WW2? What was the difference between Norway and countries like Finland and Poland, that made the Soviets wary of annexing land or occupying the northern regions?
And was there any discussions among Norway or other Allies on the possibility of a Soviet occupation or annexation of Northern Norway? Do we know what they planned for in case this happened?
It's been a while since I brushed up on my early Cold War Scandinavian history and e.g. /u/VonAdler might have better ideas here, but I believe this is one of the questions where the only person who knows the truth is Stalin. The archives in the Kremlin might shed some light unto matter, but these days they are under lock and key again, so we have to make educated guesses.
And as far as I'm aware, the old answer and the one given in the paper pretty much stands: Northern Norway was not permanently occupied most likely because of political considerations.
The way I see the events is that in 1945-46, the new order in the postwar Europe was still developing, and the birth of NATO for instance was not a foreordained conclusion, much less that Scandinavian countries would join it. In fact, there were talks of a Scandinavian defensive alliance, and it's very possible that one reason the Soviets retreated from Norway and Denmark was to influence these discussions. Norway also had a sizable Communist party, which got a boost from being associated with the Germany-smashing Soviets in the immediate post-war elections, and it is well known that the post-war Soviets gave e.g. Finland strategically timed "rewards" (such as decreasing the amount of war reparations to be paid) in order to help communists in elections. Retreating from Northern Norway would've been precisely such a "reward."
Furthermore, there was the issue of Sweden to consider: Sweden was neutral, but too much Soviet encroachment would surely push it to the Western camp. (This is likely one important reason why Stalin did not annex Finland after all.)
It should be mentioned that annexing a portion of Norway into the Soviet Union would've been different from other Soviet acquisitions during and after the war and would've been a precedent. Namely Soviet Union never occupied enough of Norway to establish communist pupper governments (as it did in Poland or Czechoslovakkia for example) and Norway wasn't a hostile country towards Soviet Union in WW2 (such as Germany, Japan, Romania etc).
Annexing a portion of a non-hostile allied country that they did not control completely would've been a precedent. Now I'm sure the Soviets did a lot of unprecedented things, but I'm just pointing out that Norwegian case is not 100% comparable to other cases in which Soviet Union did decide to acquire land.