sentences:  Reagan appointed him as ambassador to Czechoslovakia and later asked him to return to Washington in 1983 to work at the National Security Council, with the assignment to develop a negotiating strategy to end the arms race.When Mikhail Gorbachev became the leader of the Soviet Union in 1985, arms negotiations and summit meetings resumed.Matlock was appointed ambassador to the Soviet Union in 1987 and saw the last years of the Soviet Union before he retired from the Foreign Service in 1991.