Final answer:
The Soviet Union annexed Lithuania, Latvia, and Estonia in 1940.
Step-by-step explanation:
The Soviet Union annexed Lithuania, Latvia, and Estonia in 1940. Under the Molotov-Ribbentrop Pact, signed in 1939, the Soviet Union and Nazi Germany agreed to divide Eastern Europe into spheres of influence. As a result, the Baltic states were incorporated into the USSR, but they were later occupied by Germany in 1941. After liberating these territories in 1944, the Soviet Union reasserted its control over Lithuania, Latvia, and Estonia.