Invasion of West Germany
The USSR invaded West Germany on October 14th, 1991. The whole of West Germany was a part of the USSR by January, 1992.
NATO and the UN surprisingly refused to intervene until after West Germany was taken over. After the takeover, the Allies (NATO and UN) decided after long discussions that they will not stop the Soviet Union from occupying West Germany, but will declare war if the USSR advances any further. Great Britain's opinion was the same as the Soviet Unions, "The Soviet Union saved us from Germany in WW2. They Deserve all of Germany." US President George H. W. Bush said "The Cup of the Soviet Union has spilled into Europe." The United States was the only member of the Allies that was against the Soviet Union taking over West Germany.