While often portrayed as naked aggression (and morally questionable), Stalin’s pre-war actions reveal a desperate calculus – one forced upon him by Western abandonment and the looming Nazi threat.
This article examines the circumstances, motives, and timeline of these “pre-WW2 Soviet invasions.”
1. Baltic states: 1920 – 1939
The Soviet Union’s interest in the Baltic States began in the aftermath of the Russian Civil War. Following the collapse of the Russian Empire, Estonia, Latvia, and Lithuania declared independence and signed peace treaties with Soviet Russia in 1920, which recognised their sovereignty.
Throughout the 1920s and early 1930s, relations between the USSR and the Baltic States were limited and often tense, but relatively stable. However, with the rise of Nazi Germany in the mid-1930s and increasing geopolitical instability, the Soviet Union began to view the Baltic region as a strategic buffer zone essential for its western defence.
In August 1939, the USSR and Nazi Germany signed the Molotov-Ribbentrop Pact, which included secret protocols dividing Eastern Europe into spheres of influence. Under these terms, Estonia, Latvia, and later Lithuania were assigned to the Soviet sphere.
In September and October 1939, the USSR coerced the Baltic States into signing Mutual Assistance Pacts, which allowed the stationing of Soviet troops and establishment of military bases on their territory. These agreements were signed under the threat of force and were not true alliances but rather a form of soft occupation.
In June 1940, using orchestrated internal unrest and Soviet military presence as justification, the USSR invaded and fully occupied the Baltic States. Puppet governments were installed, and by August 1940, Estonia, Latvia, and Lithuania were formally annexed into the Soviet Union.
That same month, the USSR also annexed Bessarabia and Northern Bukovina from Romania, further extending its control in Eastern Europe. Western condemnation was limited, and although the League of Nations expelled the Soviet Union over its attack on Finland (see below), no major action was taken against the Soviet occupation of the Baltics.
2. Poland: 1939
The invasion of Poland in 1939 was a key event in the buildup to World War II, marked by the dual onslaught from both Nazi Germany and the Soviet Union. On 1 September 1939, Germany invaded Poland from the west, and just 16 days later, the Soviet Union invaded from the east on 17 September 1939 (following the Molotov-Ribbentrop Pact between the USSR and Germany).
2.1. Soviet position and strategic motives
The USSR’s invasion of eastern Poland was framed as a protective measure for the ethnic Ukrainians and Belarusians living in the region, but the reality was that the Soviets were keen to secure a buffer zone between themselves and Germany (pushing the frontier 200km west before the inevitable German conflict). This move was driven by the same logic that informed many of Stalin’s actions: the need to protect Leningrad (modern-day St. Petersburg) from future German aggression.
2.2. The secret protocol: dividing Eastern Europe
Secret clauses of the Molotov-Ribbentrop Pact divided Eastern Europe into spheres of influence between USSR and Germany. This secret teritory division is often depicted as a true conquering alliance, but its true intent was more about strategic maneuvering than ideological alignment. It allowed Stalin to act like a partner to Hitler, while secretly assuring that the Soviets would avoid a two-front war and strengthen their defenses against a growing Nazi threat.
In other words: when faced with clear (stated in Mein Kampf) German expansion threat and West’s refusal to engage in meaningful alliances or support – USSR had to buy time and make some space for defending.
2.3. Poland’s fate: betrayed on both fronts
From the Polish perspective, the Soviet invasion of eastern Poland was the final blow to a country already under attack from the German invasion. Once the Polish government fled to Romania, Poland ceased to exist as a functional state, and both the Germans and Soviets carved up the country. The Soviets justified their actions as part of a defensive maneuver, but it was clear that the division of Poland was driven by the Molotov-Ribbentrop Pact’s secret clauses.
For Poland, this was the ultimate betrayal, not just from Germany, but from the West as well. Despite Britain and France declaring war on Germany in 1939 in response to the invasion, they failed to intervene to defend Poland’s borders, leaving them to face two aggressors – Nazi Germany and the Soviet Union – without meaningful support.
3. Finland: The Winter War (1939 – 1940)
In 1939, as tensions between the Soviet Union and Nazi Germany escalated, Finland found itself caught between two powers competing for control of Eastern Europe. As the Soviet Union sought to expand its influence, especially around Leningrad, Finland, a small country with a strategic location, became a critical buffer between the Soviet Union and the rest of Europe.
3.1. Soviet Demands and Finnish Neutrality
After signing the Molotov-Ribbentrop Pact in August 1939, which divided Eastern Europe into spheres of influence, the Soviet Union sought to fortify its western defenses. The USSR’s primary concern was Leningrad, as Stalin sought to push the border further away from the city to reduce the threat of a German invasion via Finland.
Finland refused to commit to a defensive alliance or a military agreement with the USSR.
In October 1939, the Soviets offered Finland territorial concessions in exchange for land along the Karelian Isthmus. Finland, however, refused these demands too, fearing the loss of sovereignty and territorial integrity. The Soviet Union then demanded that Finland allow the USSR to build military bases on Finnish soil. Finland, under the leadership of President Kyösti Kallio, firmly rejected this as well.
3.2. The Winter War: November 1939 – March 1940
With Finland’s refusal to comply with Soviet demands, the USSR invaded Finland on 30 November 1939, in what became known as the Winter War. The Soviets’ military superiority was overwhelming, but the Finns put up fierce resistance. Despite the Soviet offensive, the Finnish army managed to hold their ground for several months, using their knowledge of the terrain and guerrilla tactics to inflict significant casualties on the Soviet forces.
Finnish ski troops, moving silently through frozen forests, became legendary for their ambush tactics against Soviet armor.
During the Winter War, Finland’s neutrality was put to the test. While the Soviets pressed their demands, Finland received little help from the West, despite Britain and France expressing support. Finland, meanwhile, had limited options and was reluctant to align itself too closely with Nazi Germany, despite their shared enemy in the Soviet Union.
3.3. The Moscow peace treaty and its aftermath
The Winter War ended on March 13, 1940, with the signing of the Moscow Peace Treaty, which forced Finland to cede significant territories to the Soviet Union, including the Karelian Isthmus and the city of Viipuri. However, Finland was able to maintain its sovereignty, despite the loss of about 10% of its territory.
While Finland had to cede land, the Soviets failed to completely crush the Finnish resistance. Finland retained its independence, which was a significant achievement in the context of the larger European power struggles at the time.
The Winter War exposed critical weaknesses in the Soviet military, notably the Red Army’s ineffective response due to the purges of the late 1930s. Stalin, expecting a quick victory, was surprised by the Finnish resistance. The war had wide-reaching effects: it convinced Hitler that the USSR was weak, influencing his decision to launch Operation Barbarossa in 1941, and it forced Soviet military reforms that helped them eventually counter Germany’s invasion.
3.4. Finland’s shift in alignment: the continuation war 1941 – 1944
After the German invasion of the Soviet Union in June 1941, Finland found itself in a difficult position. In order to protect itself from Soviet threats and reclaim the land lost during the Winter War, Finland aligned itself with Nazi Germany in what became known as the Continuation War (1941-1944). While the relationship between Nazi Germany and Finland remained largely pragmatic, Finland sought to regain its territories lost in the previous war.
This alliance was primarily strategic, not ideological. Finland’s main objective was to reclaim lost territory, not to support Nazi Germany’s larger war effort or its ideological goals.
Conclusion
In examining the Soviet pre-war occupations and actions, it’s crucial to separate strategic necessity from ideological alignment. Today, Soviet expansion is often framed/viewed as equal (if not worse) to German expansion – but although they both involved territorial acquisition, equating Soviet buffer-building with Nazi Lebensraum is like comparing a surgeon’s incision to a murderer’s stab wound – the action appears similar, but intent and consequences differ fundamentally.
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