Why did communism in the Soviet Union collapse in the late 1980s?

Consider:
•Political factors: What did leaders in the Soviet Union, the United States, and Europe do to further the fall of communism?
•Military factors: What effect did military policies and actions in the United States and in the Soviet Union have?
•Economic factors: What effect did the economic situation in the Soviet Union have?
•Social/cultural factors: What was the attitude of the people of the Soviet bloc countries? What impact did glasnost have? What was the impact of dissidents?