Question

Following World War II, the mutual defense organization known as the North Atlantic Treaty Organization was formed
because the USSR had strengthened its armed forces.
because the USSR was threatening to occupy East Germany.
because Western European nations wanted to attack the USSR.
because Western European nations had turned to communism.

Answer 1

Because the USSR had strengthened its armed forces.

NATO was created (1949) as a collective-defense alliance to deter Soviet military power and prevent further Soviet expansion into Western Europe.