Dwight D. Eisenhower
He intimidated the Soviet Union by making them believe that the United States would respond to any act of aggression with the use of nuclear weapons.  That policy is called brinkmanship, new look, and massive retaliation.  He also authorized planes to spy on the Soviet Union, but when a U.S. spy plane accidentally crashed into the Soviet Union near the end of Eisenhower's term, it hurt relations between the United States and the Soviet Union.