Tear down this wall speech. what was the cause of the Soviet Union losing its grip on its empire?

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"Tear down this wall", also known as the Berlin Wall Speech, was a speech delivered by United States President Ronald Reagan in West Berlin on June 12, 1987. Reagan called for the General Secretary of the Communist Party of the Soviet Union, Mikhail Gorbachev, to open the Berlin Wall, which had separated West and East Berlin since 1961.[1][2] The name is derived from a key line in the middle of the speech: "Mr. Gorbachev, tear down this wall!"