I'm sorry if I gave you the impression I thought the Soviets had a moral right to take Finnish territory. We're talking about what the Soviets were thinking, not what others thought of their actions. There is no indication that Stalin ever wanted to annex, or completely dominate Finland. The terms in March 1940 could've been a lot worse, Stalin wanted a neutral Finland. Stalin wasn't losing any sleep about a Franco/British army showing up in Finland. After 4 months nobody showed up, and the force that reached Norway in April was too feeble to do much, they couldn't even effectively operate cross country. Stalin's mistake was starting the Winter War to begin with. If he hadn't done that there never would've been a Continuation War. When Finland gave up again in 1944 Stalin was satisfied with taking Petsamo, and Finnish neutrality. The Allies weren't coming to Finland's aid in 1944, Stalin could've done what he wanted.
The Baltic States, and Poland were different matters. Stalin had a deep seeded grudge against the Poles going back to the War of 1920. Eastern Poland, and the Baltic States served as a buffer zone against the Germans, and improved the Soviet strategic situation. The Baltic states strengthened their position on the Baltic, and prevented anyone from blocking the Gulf of Finland. That was also another reason the Soviets had concerns about the Finns having bases on the Gulf of Finland. To say that the Baltic States were just defenseless, is in a way to explain why Stalin took them, not a moral justification for the action. Stalin was an evil, ruthless man, but he was always cautious, and his grand strategy was defensive. He was never a reckless gambler like Hitler. Of course that was still unclear in 1939, so it's understandable that the Allies didn't understand his goals were limited.
Even though Stalin was a Georgian he was an extreme Russian Nationalist. Eastern Poland had been part of Czarist Russia, and was the home of many Ukrainians, and other Soviet ethnic groups. Stalin essentially ethnically cleansed the region, and tried to decapitate the Polish elite. The Katyn Wood was only a part of Stalin crimes against the Poles. In 1945 Stalin accepted an independent Poland, under Communist control, with the 1939 Eastern border. Poland was given Eastern Germany to create a wider buffer zone against a future German invasion. Bessarabia had also been part of Czarist Russia, so part of this was Soviet resentment of Versailles. Stalin also got a measure of pleasure in 1945 by avenging the Russian defeat in the Russo/Japanese War.
About the bolded points, you are simply wrong. There is a lot of evidence of Stalin wanting to take over whole of Finland, beginning with the fact that when the Soviet attack begun on November 30, 1939, the USSR proclaimed that it no longer recognized Finland's legal government, but that there was a "Finnish Democratic government" it now saw as legally leading Finland - the so-called Terijoki government, a Soviet puppet led by a Finnish emigrant Communist. Until January 1940, Stalin then would not recognize the Finnish government diplomatically. The intent there is clear: at the beginning of the war, Stalin had abandoned the idea of a diplomatic solution with an independent Finland, and was committed to put his pet "Finnish Democratic government" in power in Helsinki. Only after Finland could not be conquered as fast as Stalin had planned, with the Red Army failing in the task given to it, Stalin again opened the possibility for a diplomatic solution with the Finns.
Other information pointing towards the aim to conquer all of Finland was, for example, the guide book on Finland issued to the Red Army in the run-up to the war that included specific information about all the parts of the country with helpful specifics like how not to mistakenly cross over to Sweden at the Finno-Swedish border and while there, to remember to be courteous to the Swedish border guards... Also, when we look at the Molotov-Ribbentrop Pact's secret protocol (in its amended form), with the exception of Finland all the other areas placed in the Soviet sphere of influence in 1939 were annexed directly into the USSR by 1941.
Given especially the fate of the Baltic states, which also got puppet governments that then "voluntarily" asked to join the USSR, it seems quite likely that a similar fate had been prepared for Finland had the Red Army completed the conquest of Finland by the end of 1940 like was planned. Without the Finnish government's refusal to hand over border areas to the USSR in the fall of 1939, the likeliest outcome for 39-40 would have been a similar creeping takeover for Finland like happened in the Baltic states that did accept the Soviet demands made in the same timeframe.
The history of the Winter War, and the role of Finland in WWII in general, is a heavily researched subject. Historians in Finnish universities and academia have studied the Winter War in depth, and understandably in more detail than, say, US or British historians have. Right now, I believe that it is the generally accepted consensus among Finnish professional historians that 1) Stalin's original goal in the Winter War was to conquer all of Finland, and 2) that the possibility of an Allied intervention was the key reason why Stalin in the end in March 1940 decided to make peace with Finland with only very limited gains for the USSR. Without such an outside factor to the equation, it would not even have been logical for the USSR to end the war when it did, after what had been a humiliating showing for the Red Army, at a point in time when the Soviets were actually finally winning the war, and were only mere weeks away from breaking the Finnish army for good.
The most recent book examining this issue, by a professional historian, was published in 2016. In his book
Stalin ja Suomen kohtalo ("Stalin and the Fate of Finland"), Kimmo Rentola, Helsinki University history professor and highly respected researcher, argues the point about the crucial role played by the Allied intervention plans in making Stalin stop the attack, based on a good number of primary and secondary sources, also official documents from the former Soviet archives. Rentola had also published practically the same research earlier in
a peer-reviewed article in English in
The International History Review.
According to Rentola's research, Stalin truly believed that an Allied intervention in support of Finland was imminent in early March 1940. This was in big part due to Stalin being, in the event, reliant on intelligence information from France, where the discussion about the intervention was overtly and unrealistically positive, making it seem actually likely, whereas he was temporarily not receiving information from his intelligence operatives in Britain, which would have likely made him understand that it was actually unlikely that the intervention would be realized. This apprehension about the Allies joining the war on the Finnish side was what made him hurry the peace deal with the Finns, even while he knew that the Finnish army was on its last legs and that total victory was very close. The argument about Stalin thinking that he needs to wrap up the Winter War early to avoid it escalating into a war against the British and the French is very much not a fringe theory, but a source-based result of professional historical research based also on a pre-existing corpus made of decades of Finnish academic historiography.
Notably, Rentola's book has received nothing but positive reviews from Finnish professonal historians, and was also given a national nonfiction prize in 2017.
What stands out from Rentola's treatment in the book in general is that a) Stalin apparently never had a "masterplan" for Europe, but his plans were changing all the time, depending on changing circumstances, and b) the events of the Winter War were the crucial thing that branded the relations between Stalin and the Finnish leadership in 1940-1953. To read Rentola's book, it then appears that it was only through the Winter War that Finland became a "special case" for Stalin - the Finnish will and ability to put up a resistance apparently had a significant effect on him in terms of how he viewed Finland. Before that, we might argue that he viewed Finland in the same light as the Baltic states, only differing from them in terms of its more northern and on balance more peripheral geographical position, not in terms of the justification of its national existence. After early 1940, though, Stalin apparently had a grudging respect towards Finland, in that the nation apparently could put up a credible defence, and then attract foreign support for its cause (as manifested in the Allied intervention plans during the Winter War, of which Stalin apparently had a distorted view).
Stalin's treatment of Finland during the Continuation War and after it should then be seen in this light, especially as his view about the Finnish will and ability to defend themselves was probably reaffirmed through the battles of the summer of 1944. But, if we accept Rentola's thesis, we should not project this acceptance by Stalin to treat Finland as a special case into the pre-Winter War situation, or into a TL where there is not Winter War, especially to one where the Finns would cave in to Soviet demands in 38-39. In such a TL, Stalin would have much less will to treat Finland in an almost cordial fashion. We need to remember that even if it is sometimes claimed that Stalin "always" had a bit of a soft spot for Finland, in the purges he absolutely decimated the cadres of Finnish Communist leaders and civil warriors who had escaped into Soviet Russia post-1918.
Understanding history is about getting into the heads of people, and understanding their motivations, and thinking. Just reading about what enemies thought about a leader's intentions at the time isn't understanding the big picture. You have to take into account what both sides were thinking. The Finns may have feared a Soviet take over, but that doesn't make it true. In 1940 did Stalin even know the Allies were going to land in Norway? He could have overrun Finland twice, but chose not to do it. It was better for it to be neutral, and not have to occupy it.
I agree with the bolded idea. And because of that, I must invite you to reconsider your understanding about how Stalin viewed the Finns, and what his goals were in Finland, based on actual historical research, not guesswork. Before and in 1939, Stalin did not want Finland to be neutral, he wanted to conquer Finland and make it a part of the Soviet sphere, occupied by Soviet troops. But then Finland's ability to survive through the Winter War, especially, and then the Continuation War, too, made Stalin grudgingly accept the value of Finland being a neutral country on the USSR's northwestern flank. Simply put, trying to take Finland over directly had proven more trouble than it was worth.
