The timeline of the occupation of the Baltic states lists key events in the military occupation of the three countries – Estonia, Latvia and Lithuania – by the Soviet Union and by Nazi Germany during World War II.
1939
20 March 1939, German ultimatum to Lithuania was an oral ultimatum presented to Juozas Urbšys, foreign minister of Lithuania, by Joachim von Ribbentrop, foreign minister of Nazi Germany. The Germans demanded that Lithuania give up the Klaipėda region (Memelland), or the Wehrmacht would invade Lithuania. 23 August 1939, Molotov–Ribbentrop Pact (Nazi-Soviet Alliance) signed. A secret protocol of the pact places Estonia, Latvia, and Finland in Soviet sphere of interest, Lithuania in Germany's sphere of influence. Poland was effectively divided between Stalin and Hitler. 1 September 1939, Nazi Germany invades Poland. This event signifies the start of World War II in Europe. 14 September 1939, Polish submarine Orzeł enters Tallinn harbour (in then neutral Estonia), crew interned. 17 September 1939, Soviet Union invades Poland, cooperating with Germany as agreed in the Nazi-Soviet Alliance. 18 September 1939, the Polish submarine Orzeł escapes from Tallinn, sets course to Great Britain. 22 September 1939, Soviet army captures the region of Vilnius, which Poland had annexed from Lithuania in 1922. 24 September 1939, Stalin demands establishment of Soviet military bases in neutral Estonia, using the Orzeł incident as the pretext and threatening with war in case of noncompliance. 28 September 1939, Molotov–Ribbentrop Pact amended pursuant to German-Soviet Boundary and Friendship Treaty; most of Lithuania now falls into the Soviet "sphere of influence". 28 September 1939 Estonia submits to Soviet ultimatum, accepts military bases. 2 October 1939, Soviet Union demands establishment of military bases in neutral Latvia, threatening with invasion in case of noncompliance. 5 October 1939, Latvia submits to Soviet ultimatum, accepts military bases. 5 October 1939, Soviet Union begins negotiating with Finland for bases and territory exchanges. 10 October 1939, Lithuania accepts Soviet bases. Soviet Union transfers control over the Vilnius region to Lithuania. 18 October 1939, First Soviet units move into the designated military bases in Estonia. 13 November 1939, Finland rejects Soviet ultimatum. 30 November 1939, Soviet Union invades Finland. Winter War starts. 1 December 1939, Terijoki government, Soviet puppet government of Finland created in the Terijoki county captured from Finland. 14 December 1939, League of Nations expels Soviet Union for its illegal war against Finland.