Question

What accounts for why the Soviet Union decided to formalize its East European alliance through the Warsaw Pact?

Answer 1

The primary reason why the Soviet Union decided to formalize its East European alliance through the Warsaw Pact was because the US had done a similar thing in the west with NATO. 

Answer 2

Answer: To establish the counterpart to the Western NATO alliance.

Explanation: After WWII and the division of interest zones, the Soviet Union began to impose communism in East European countries. The whole situation led to the Cold War, because the Western Allies did not want to strengthen and spread Communism. Western European countries conducted democratic elections and were gathered around the NATO military alliance in order to prevent communism. Stalin gathered all the Eastern countries around the Warsaw Pact, that is, the military alliance, and thus formalized the Eastern European Alliance as an alliance opposed to the Western Allies.