Question

After World War II, why did the Soviet Union take over a number of countries to its west?
to create a buffer zone between itself and the Western powers
to build an empire to rival that of enemies such as the United States
to punish Germany for its aggression during the war
to ensure compliance with the Declaration on Liberated Europe

Answer 1

to create a buffer zone between itself and the Western powers

The USSR established Soviet-controlled governments in Eastern Europe mainly to provide strategic depth and security against future invasions (and to secure a sphere of influence), rather than to punish Germany or to follow the Declaration on Liberated Europe.