text: In the 1980s , the glasnost liberalisation of Soviet society provoked KGB Chairman Vladimir Kryuchkov ( 1988 â `` 91 ) to lead the August 1991 Soviet coup d' Ã tat attempt to depose President Mikhail Gorbachev .
simplified: The KGB ended when its chief , Colonel-General Vladimir Kryuchkov , used the KGB 's resources to help the August 1991 coup attempt to overthrow Soviet President Mikhail Gorbachev .