Final answer:
The Soviet Union built the Berlin Wall in 1961 to prevent East Germans from migrating to the West and to symbolize the division between East and West during the Cold War.
Step-by-step explanation:
The Soviet Union built a wall around West Berlin in 1961 to halt the migration of East Germans to the West. The construction of the Berlin Wall was a defensive measure to prevent East Berliners from leaving the Soviet sector of the city. It became a powerful symbol of the Cold War and the division between the Communist East and the Capitalist West.