Joseph Stalin

=== 1939–1941: Pact with Nazi Germany ===
As a Marxist–Leninist, Stalin considered conflict between competing capitalist powers inevitable; after Nazi Germany [[Anschluss|annexed Austria]] and then [[German occupation of Czechoslovakia|part of Czechoslovakia]] in 1938, he recognised a war was looming.{{sfn|Montefiore|2003|p=308}} He sought to maintain Soviet neutrality, hoping that a German war against France and Britain would lead to Soviet dominance in Europe.{{sfnm|1a1=Conquest|1y=1991|1pp=220–221|2a1=Service|2y=2004|2pp=380–381}} Militarily, the Soviets also faced a threat from the east, with Soviet troops [[Soviet–Japanese border conflicts|clashing with the expansionist Japanese]] in the latter part of the 1930s.{{sfnm|1a1=Service|1y=2004|1pp=392–393|2a1=Khlevniuk|2y=2015|2pp=163, 168–169}} Stalin initiated a military build-up, with the Red Army more than doubling between January 1939 and June 1941, although in its haste to expand many of its officers were poorly trained.{{sfn|Khlevniuk|2015|pp=185–186}} Between 1940 and 1941 he also purged the military, leaving it with a severe shortage of trained officers when war broke out.{{sfn|Conquest|1991|pp=232–233, 236}}

[[File:Bundesarchiv Bild 183-H27337, Moskau, Stalin und Ribbentrop im Kreml.jpg|thumb|upright=0.8|left|Stalin greeting the German foreign minister [[Joachim von Ribbentrop]] in the Kremlin, 1939]]
As Britain and France seemed unwilling to commit to an alliance with the Soviet Union, Stalin saw a better deal with the Germans.{{sfn|Service|2004|pp=399–400}} On 3 May 1939, Stalin replaced his western-oriented foreign minister [[Maxim Litvinov]] with [[Vyacheslav Molotov]].{{sfn|Nekrich|1997|p=109}} Germany began negotiations with the Soviets, proposing that Eastern Europe be divided between the two powers.{{sfnm|1a1=Conquest|1y=1991|1p=220|2a1=Khlevniuk|2y=2015|2p=166}} Stalin saw this as an opportunity both for territorial expansion and temporary peace with Germany.{{sfnm|1a1=Conquest|1y=1991|1p=220|2a1=Khlevniuk|2y=2015|2pp=168, 169}} In August 1939, the Soviet Union signed the [[Molotov–Ribbentrop pact]] with Germany, a non-aggression pact negotiated by Molotov and German foreign minister [[Joachim von Ribbentrop]].{{sfnm|1a1=Conquest|1y=1991|1p=221|2a1=Roberts|2y=1992|2pp=57–78|3a1=Service|3y=2004|3p=399|4a1=Khlevniuk|4y=2015|4p=166}} A week later, [[Germany invaded Poland]], sparking the UK and France to declare war on Germany.{{sfnm|1a1=Conquest|1y=1991|1p=222|2a1=Roberts|2y=1992|2pp=57–78|3a1=Khlevniuk|3y=2015|3p=169}} On 17 September, [[Soviet invasion of Poland|the Red Army entered eastern Poland]], officially to restore order amid the collapse of the Polish state.{{sfnm|1a1=Conquest|1y=1991|1p=222|2a1=Roberts|2y=2006|2p=43}} On 28 September, Germany and the Soviet Union exchanged some of their newly conquered territories; Germany gained the linguistically Polish-dominated areas of Lublin Province and part of Warsaw Province while the Soviets gained Lithuania.{{sfnm|1a1=Conquest|1y=1991|1p=223|2a1=Service|2y=2004|2pp=402–403|3a1=Wettig|3y=2008|3p=20}} A [[German–Soviet Frontier Treaty]] was signed shortly after, in Stalin's presence.{{sfn|Conquest|1991|p=224}} The two states [[Nazi–Soviet economic relations (1934–41)|continued trading]], undermining the [[Blockade of Germany (1939–1945)|British blockade of Germany]].{{sfnm|1a1=Conquest|1y=1991|1p=224|2a1=Service|2y=2004|2p=405}}

The Soviets further demanded parts of eastern Finland, but the Finnish government refused. The [[Winter War|Soviets invaded Finland]] in November 1939, yet despite numerical inferiority, the Finns kept the Red Army at bay.{{sfnm|1a1=Conquest|1y=1991|1p=228|2a1=Service|2y=2004|2p=403|3a1=Khlevniuk|3y=2015|3pp=172–173}} International opinion backed Finland, with the Soviets being expelled from the League of Nations.{{sfnm|1a1=Conquest|1y=1991|1p=279|2a1=Khlevniuk|2y=2015|2p=173}} Embarrassed by their inability to defeat the Finns, the Soviets signed an [[Moscow Peace Treaty|interim peace treaty]], in which they received territorial concessions from Finland.{{sfnm|1a1=Service|1y=2004|1p=403|2a1=Khlevniuk|2y=2015|2p=173}} In June 1940, the Red Army occupied the Baltic states, which were forcibly [[Occupation of the Baltic states|merged into the Soviet Union]] in August;{{sfnm|1a1=Conquest|1y=1991|1p=227|2a1=Service|2y=2004|2pp=404–405|3a1=Wettig|3y=2008|3pp=20–21|4a1=Khlevniuk|4y=2015|4p=173}} they also invaded and annexed [[Soviet occupation of Bessarabia and northern Bukovina|Bessarabia and northern Bukovina]], parts of Romania.{{sfnm|1a1=Brackman|1y=2001|1p=341|2a1=Khlevniuk|2y=2015|2p=173}} The Soviets sought to forestall dissent in these new East European territories with mass repressions.{{sfn|Khlevniuk|2015|p=170}} One of the most noted instances was the [[Katyn massacre]] of April and May 1940, in which around 22,000 members of the Polish armed forces, police, and intelligentsia were executed.{{sfnm|1a1=Conquest|1y=1991|1p=229|2a1=Khlevniuk|2y=2015|2p=170}}

The speed of the German victory over and occupation of France in mid-1940 took Stalin by surprise.{{sfnm|1a1=Conquest|1y=1991|1p=229|2a1=Service|2y=2004|2p=405}} He increasingly focused on appeasement with the Germans to delay any conflict with them.{{sfnm|1a1=Conquest|1y=1991|1p=229|2a1=Service|2y=2004|2p=406}} After the [[Tripartite Pact]] was signed by [[Axis Powers]] Germany, Japan, and Italy in October 1940, Stalin proposed that [[German–Soviet Axis talks|the USSR also join the Axis alliance]].{{sfnm|1a1=Conquest|1y=1991|1p=231|2a1=Brackman|2y=2001|2pp=341, 343|3a1=Roberts|3y=2006|3p=58}} To demonstrate peaceful intentions toward Germany, in April 1941 the Soviets signed [[Soviet–Japanese Neutrality Pact|a neutrality pact]] with Japan.{{sfnm|1a1=Conquest|1y=1991|1p=233|2a1=Roberts|2y=2006|2p=63}} Although ''de facto'' head of government for a decade and a half, Stalin concluded that relations with Germany had deteriorated to such an extent that he needed to deal with the problem as ''de jure'' head of government as well: on 6 May, Stalin replaced Molotov as [[Premier of the Soviet Union]].{{sfnm|1a1=Conquest|1y=1991|1p=234|2a1=Khlevniuk|2y=2015|2p=180}}