One dark reality is Stalin's anti-Semitic overture to Hitler: he appointed Vyacheslav Molotov in May 1939, shortly before the pact, as a replacement for Maxim Litvinov, who was of Polish-Jewish background.
It is also curious that the territory Stalin took under the agreement roughly corresponds to tsarist Russia's acquisitions under the Partitions of Poland (1772-95). And most of that territory remained part of the Soviet Union after the war. In fact, Stalin took yet more land from Poland in the conflict’s aftermath, “compensating” with formerly German-majority areas such as East Prussia. Quite perversely, he also grabbed that part of East Prussia, formerly known as Königsberg, and re-dubbed it Kaliningrad, now an important Baltic outpost of the Russian navy.
The accompanying ethnic cleansing included de-Germanizing land given to Poland, and moving Poles from western portions of today’s Ukraine and Belarus, and placing them in the formerly German areas of western Poland. Naturally, these policies exacerbated an already-massive post-war refugee crisis.
I became somewhat more acutely aware of these issues two years ago when translating a letter from Rusyn. The author had lived in Transcarpathian Ruthenia, which had belonged to Czechoslovakia during the interwar period and was reassigned to the Ukrainian SSR in 1945. But she also had relatives in the southeast corner of Poland, and there were things she dealt with only obliquely in the letter for fear of reprisals. The content of the letter was in a variant of Rusyn written in a Hungarianised Latin alphabet - in which a gy combination represents a "soft" or palatal d sound, for instance - probably so that officials opening and reading their mail would be unable to read it, or it would be too much trouble to find someone who could.
This writing, having originated during the late 1800s in the old Austro-Hungarian Empire, was only known to the oldest generation at that time. Yet on the envelope, both the recipient and return address were written in flawless Russian cursive, which some grandchild had doubtless learned in school - despite the fact that this was the western-most territory of Ukraine!
As a Ukrainian-American friend and scholar once told me, this part of Ukraine had for centuries been under Polish or Austrian rule and until the immediate post-war period "had not been touched by the Russian language or culture." As long-term history goes, this Russification represented part of a relatively recent westward movement of Muscovite influence, which was only halted - and reversed - by the fall of the Berlin Wall in 1989.
In spite of this tendency, the Polish population of the Grodno region, for example, one of the most heavily Polish areas attached to Belarus, has managed to survive. It has even thrived in the years following the dissolution of the USSR and now stands at around 230,000. But how it will fare under the very Moscow-friendly Lukashenko remains to be seen.
Yes, Muscovy has over the centuries expanded both eastward and westward, as well as southward into the Caucasus and Black Sea region, not to mention two unsuccessful attempts in the 19th and 20th centuries to spread its influence into Afghanistan. This has been going on from Ivan the Terrible, to Peter the Great, to Catherine the Great and beyond. But, one might well ask, at what expense to non-Russian nationalities? The Ottoman Empire did much the same, but look at it now. Who says Russia's expansionism isn't reversible?
[Note: this post was edited for thoroughness and clarity on 20 Aug. 2024, but no changes were made to reflect on Putin's 2022 invasion of Ukraine. That said, it may now read a bit more as if anticipating that incursion.]