One of the effects of this massive buildup of American military might during the 1980s was pressure inside of the Soviet Union to match the United States. However, internal pressures inside the Soviet Union for increased freedoms, along with economic pressures led to the loosening of their control in Eastern Europe. In 1989, one by one of these nations in Eastern Europe began to rebel against their Communist governments, leading to the opening of the Berlin Wall in November. The mighty Warsaw Pact as well as the Soviet Union was crumbling from within.