What do you consider to have been the main aims of the Soviet foreign policy in the years 1945-1956?
I would argue that there were three major aims of Soviet foreign policy during this time period.
First, the Soviet Union was determined to create a "buffer zone" between itself and the West. It had been invaded from the West in 1812 and again in 1941 and it feared the possibility of another such invasion. Having a buffer zone would make it much harder for Western countries to attack.
Second, the Soviet Union wanted to spread communism as much as possible. This was a major factor behind Soviet support for Mao Zedong in China and for Kim Il-Sung in North Korea.
Finally, the Soviet Union was seeking to increase its control over its satellite states in Eastern Europe. The Soviets were not content to simply have communist countries in Eastern Europe. Instead, they also wanted control of those countries. It was for this reason that they instituted things like Cominform and Comecon, which tied the satellite nations more closely to the Soviet Union.