 Complete the following phrase:  The President of the Union of Soviet Socialist Republics , also known as the President of the Soviet Union ,  or the President of the USSR , was the head of state of the Union of Soviet Socialist Republics from 15 March 1990 to 25 December 1991. Mikhail Gorbachev was the only person to occupy this office. Gorbachev was also General Secretary of the Communist Party of the Soviet Union between March 1985 and August 1991. He derived an increasingly greater share of his power from his position as president until he finally resigned as General Secretary after the 